I'll second the good word for Dragon Caving Gear... I got an oversuit from them over 3 years ago. They custom made it for me (i'm tall and skinny) and gave it to me for the same price as an off the rack one... about 50 quid in 2003.
It's survived 3 years of pretty hard caving, the only thing i've had to do is re-sew one of the neoprene cuffs on the left sleeve... it takes abuse when i pull it back to look at my watch... and there's a small hole that's just started to form in the inside seam of the right knee. But that'd it... no holes in the seat, the front of the knees, the elbows, or anything like that... It's made of 1000denier cordura.
If you're in the UK or willing to pay postage, It's probably worth giving Dudly a call...