Which sleeping bag?

Yes I think panniers are horribly heavy compared to other gear. Ortlieb Classic front and rear panniers plus a front rack are a total of some 4 kg, or some 15-20% of your luggage weight. Compare that to your tent. It is therefore that I try to keep my luggage volume down to where I only need rear panniers. With an expensive compact sleep system like a 200 pound (in the sale) PHD Minimus 300 and a compact mattres like the Neoair All Season you do not need the heavy and expensive front panniers plus rack (2-2.5 kg at some 125 pounds). At just over 1 kg the sleep system in itself is at least another kilogram lighter than many other cheaper sleep systems. So for roughly the same budget as a more traditional outfit you loose 3 kg, which is a difference that you will notice. If the budget is tighter, an Alpit Pidedream 400 and an Exped Synmat Basic will still do the same trick.
Willem

Agreed re storing the down bags. My PHD ones come with a compression bag for travel and a large mesh bag for storage

Personally I would not pay another £100 to lose less weight than i can achieve by drinking the contents of one of my water bottles (as i by default tour with 4 panniers - space is not too much of a problem -although i have considered adding a trailer) - i have a relatively cheap north face down bag - my priorities with a sleeping bag are

1. is it going to be warm enough or too warm for that matter (one shortish july tour in france where i knew it was going to be warm i just took a £5 bag i bought in Tescos)
2. has it got a good quality zip of sufficient length that when it is warmer i can have good ventilation
3. is it big enough that i can sleep in it comfortably - ie get all of me in when it cold
4. is it made of a relatively durable material that feels nice to sleep in and will withstand being packed at least a 100 times and a few trips through a washing machine

I've got an ex military bivvy bag, pretty light and folds down small. Put any sleeping bag in it (think i use some crappy aldi one) and you are toasty for the night. Might be a bit overkill inside a tent, and it isn't as pretty as the outdoor emporium stock, but for 12 quid you can't go wrong.

Pipedream 400 currently in stock. If you want one, act soon. I would expect them to have run out within a month.

I have the http://www.gelert.com/products/x-treme_lite_1200_sleeping_bag 3 season 1.5kg, rolls up pretty small and is around £50 so a lot cheaper than down.

I can appreciate that not everyone has tons of money, not everyone wants to whittle the weigh down to 450g like me, but this "1.5kg" bag will almost certainly turn out a) to weigh more (about 1600g at a guess) and b) the weight will not include the compression bag which will be 100g+. So it is a very very heavy bag, and "rolls up pretty small" is not borne out my the dimensions shown.

I say all this not to criticise your choice, but in case newbies reading this do not head the advice of the many experienced tourers who know that a few hundred grams here and there soon add up to a lot of weight, extra panniers, and ultimately a much less happy tour.....

The Op did ask for mid budget, and imo £50 would be low mid budget, and so to give more details weighs in at 1516g stuff sack included, size wise just measured in at 32cm long x 22cm wide.

I will stick to this as being a decent mid range 3 season sleeping bag. I do appreciate every gram counts but on a mid budget you could do a lot worse.

No, sorry but no.
You can't possibly know what makes others happy, how can you? Congratulations on finding what works for you, and I'm glad to see you share it. But the idea that because it works for you it must for everyone else is nothing short of absurd. My parents toured with woolen blankets, canvas ridge tent, brass primus and the saucepan and frypan from the kitchen, they were still talking about it forty years later, not an unhappy experience. My happiest tour involved carrying the gear for two, we just adjusted the mileages to suite. Have a look at some of the loads being carried on the loaded touring bikes website, are they all so much less happy?
The only thing that has ever hampered the enjoyment of touring for me has been not getting a good nights sleep. My sleeping kit weighs more than my tent and I'm happy to carry it.

EDIT - To illustrate my point, just go have a look at the photos on the round the world bike race thread. Some riders with four panniers, some with two, some with frame bags, others with bits just bungeed on... all of these riders will have thought long and hard about what to carry, and come to different conclusions.

fair enough.

It all depends on what you want to do. You really do not need more than a cheap synthetic bag if you only tour in the Mediterranean in summer. Equally, only a very serious down bag will do for a cross continental trek through Mongolia or in the Andes. So the extremes are easy. But what if you camp in the UK in early Spring and late Autumn, or in Europe at higher elevations? For that I would argue that a bag with an honest temperature rating to a few degrees freezing is about right, plus a couple of degrees margin if you are a cold sleeper. Cheap bags quite simply do not go that low, unless they are enormous. Now you may argue that a large size and heavy weight do not matter, but they come at a price because pannier space does not come free. If the cheap large sleeping bag means that you need an otherwise unnecessary set of front panniers you will have spent more than the cost of a better sleeping bag. Moreover, down bags last much longer than even good quality synthetic bags, and that is a sound economic argument in itself.
For me mid budget for this temperature is the range Alpkit Skyhigh at the lower end to PHD sale prices at the upper end. The 200 pounds that was indicated as a budget should buy a Minimus 300 or 500 (almost) in the upcoming sale, I should think. If you think that is too much, go for an Alpkit Pipedream (but watch the volume).
Willem

Wow, it might be cheaper to hire your own Sherpa.

The Polish brand Cumulus are another highly respected and sharply priced possibility: http://www.sleepingbags-cumulus.com/down-sleeping-bags.html You order directly from Poland.
Willem

Quite agree. Some of the worst nights on my cross the USA trip were when my sleeping pad had a leak near the valve that couldn't be fixed, and I was days away from somewhere I could buy a new one. Every night camped out was waking up and turning over every hour. Then I'd have to bike for eight hours. Not fun.

I read up on the ultralight camping websites to find a replacement pad. I ended up with a Big Agnes insulated air core pad. It is 2.5" thick and is 6' long weighing about 1 lb. My previous pad was 1 lb and only 3/4 length (40" long) and 1" thick. The thicker, longer pad made a big difference in sleeping well besides just staying inflated all night.

In choosing a down bag, fill weight is important. If you buy a 600 or 500 fill weight bag, you might as well buy a synthetic because it will weigh pretty much the same amount for less money, and both bags will compress about the same. I have a Sierra Designs Spark 800 fill weight ultralight sleeping bag rated to 15 F. It weighs 2 lbs and compresses into a ball about 6" in diameter. The ultralight basically just means it is a half zipper. The half zipper is annoying when it is a bit too warm for the bag because you can't really unzip the bag -- you are either in the bag, or you are out. I also usually carry a silk liner as it is light, small and adds about 5-10 deg if I need it, or I can use it outside the bag when it is warm.

The size of a sleeping bag is also very important. If it is too large, you won't be able to heat up the space inside and will be cold. I bought a woman's sleeping bag because I am 5'5" tall, and men's bags are all 6' meaning not only would it be cold, but I'd be carrying around extra weight I don't need. Women's bags have extra room in the hips which is nice for turning over inside the bag.

I also bought a Big Agnes Fly Creek UL 2 on recommendation from another cyclist I met. I had been carrying a fly-only one man ultralight tent that came in at just under two pounds, but didn't provide much protection from rain or insects. This tent weighed only slightly more but had twice the room and provided good protection from the rain. It was expensive but definitely worth it, and will last me for many years to come.