i really feel for you Susie, i REALLY do. I was exactly as you were, worried he's lose weight, but its amazing how quickly they can pick it up from reading on here. I joined in a period when there were about 10 -15 hay threads a week popping up, so i learnt quite quickly.
From what i've read on here, i wonder if it would be posssible to up his readigrass amount (you say he loves this?) and cut the pellets a little, as it has the same chewing effect that eating hay is (after all, hay and grass, same chewing action) then slowly decrease the reagigrass and increase regular hay.
The sample pack from 'Animal Magic Pet Supplies' is no longer available unfortunately, but they do the packs individually for 50p each
http://www.animalmagicpetsupplies.c...n_GB/?ViewAction=View&ObjectID=8496866&Page=2
Western Timothy hay (we discussed this yesterday i think?) is my pairs new favourite and smells GORGEOUS and they devour it. Might be worth trying?