you really get very little allowance for clothing....put it this way we put down £150p/m for 2 adults and 3 children, this (i think) is still over the limit (havent heard back from them yet) but the best advice is to put down as much as (reasonably) possible, the most they'll do is not it down a bit and if your lucky they may accept it.....someone on here has a link to the guidelines hopefully they'll be along soon to advise.
We are a family of 2 adults and 4 children and we put down £92 for clothing which was accepted. I did put quite alot down for school expenses though which included school uniform. Good luck.