Just a tip. I got fed up being ripped by flying suit prices so I popped into my local "work wear" shop. They do proper no messing flame retardent suits (OK boiler suits but they have all the zips and pockets of a flying suit, including a zipped front) for about £25. These are sized for builders so plently of space(!!) for underclothes and space to move arms, legs, neck etc and what is more I believe the flame retardency (if thats a word) doesnt wash out anywhere near as quickly as with the RAF standard suit.
It seems like the classic case of anything related to aviation costing 3 times more than it would otherwise!!