I'm a 42" chest and persevering with the medium I picked up on here for £65, I don't think I'll be able to wear it through winter though as there's not a lot of room left for layering up. Good for 3 season though
Tamarak said the xl should be OK. I guess the large would be OK too but I like a bit of room so I'll go with the XL. I'm 5'11", 44" chest and best part of 15 stone. I'll probably have a Buffalo Tecmax shirt and Rab duvet on underneath.
Plenty of room in the XL and not too baggy even after I slimmed down to 90kg/14 stone.