www.snugpak.com
I can say with full recommendation, to go for the SNUGPAK line of sleeping bags.These are the bags that i bought and used extensively when i was in the forces.They do a huge range of equipment,but these are the two i have used....have a look at their SLEEKA JACKET,exceptional warmth..warm when soaked through...dry it minutes..packs down to nothing and lightweight,i always carry one of this with everywhere i travel....ideal for when you get caught out in the cold.
The Special Forces Antartica 2 series, i used down to -58 ....this is their highest rated bag,Mummy design..packs down to a cylinder about 30cm long and 20cm wide....a bit over the top unless you are in the Arctic circle.
The SOFTIE MERLIN 3 range are a far better bet for the use you intend.
These come in very fetching colours ( Bright pink and blue is the one i have ) and are rated as a 2-3 season bag and are also the mummy design...you just have your nose poking out when its cold.....most importantly they pack away to something just larger than a CAN OF COKE,and weigh 900gms.
And the most important piece of sleeping bag equipment is A SILK SLEEPING BAG LINER....one of these effectively adds an extra season rating to your sleeping bag,keeps the main bag clean and protects it from wear.And also lets you join a toga party,as it can be used as an emergency toga.....most importantly again...a good quality one scrunches down to just bigger than a pack of 20 fags.
Merlin 3......large can of coke
Silk Liner....Pack of fags
you cannot get better than that.
Rollmats are also very important for comfort and insulation,if you have the old foam type ( inflatable are heavy and expensive ) and old army trick is to cut the rollmat down so it is the width and length from your head to your arse....this is the part that needs to be insulated...the length of your legs doesnt need the insulation or the supposed comfort,and youve just saved weight and space.