Try Aldi if there is one near you and they have their baby clothes in.
I've just bought some trousers yesterday for Caitlin as I only started cloth when Anna was 8 months and all her trousers are too tight for Caitlins big bum but these are very roomy compared, and reasonably cheap!
The jogging pants from asda are fab and T can still wear his 3-6 with plenty of room. Although he is a slim little thing (don't know where he gets that from!). I find Debenhams to be quite small in general for their clothes - so I avoid them now for the most part.