sleeping: We use sleeping bag, I think its tog 1.5, ds has short sleeved vest and sleepsuit,scratch mittens as he scratches himself a lot and it helps with cold hands as well. In our bedroom is around 19-20 degrees but sometimes it dropes during night to 18.5, so we have a blanket ready for him.
Ds is 6 weeks and 3 days, sleeping usually 4 hours, then 2.5 or 3,then 1.5. After second feed its really hard to get him back to sleep,sometimes he's awake for up to 2 hours. Also he's very active and noisy even during sleep,so all that kicking and grunting keeps me awake.
In our family, I'm lucky that Dh helps a lot when he's home from work. If he has a later shift and doesnt have to get up early, he does some night feeds and nappy changing. When he comes home from work, I let him have a while to relax,later he helps me so I can get something to eat without interuption and get a shower,sterilize bottles or whatever else I need to do.
I'm still amazed how good he's doing with ds when I realize he'd never even hold a baby before. He was keen to learn how to change nappy, feed him,he bathed him 4 times (twice absolutely alone)
Lately he's just been sitting with laptop and playing games for hours and hours every day,which drives me crazy, and then he's not that willing to do something around ds,but when I get angry at him, he better goes (well,sometimes) 
Cot Mattress: We have one from Kiddicare and we're happy with it. Ds not sleeping in cot bed yet as we couldnt fit it in our bedroom but mattress looks very good quality and firm enough. Wasnt very expensive as got it in sale and had excellent reviews.