Thanks all for your help, unfortunately my gorgeous Blackberry died today - really upset. Normally I am quite pragmatic about these things but I picked her because she was so lovely rather than for laying qualities or any practical reasons. Yesterday she was walking around the kitchen with me, then when I got home this lunch time she was lying in the cage at a really awkward angle but still breathing, I picked her up and held her but she was dead within minuets, first time I've cried over a hen!
Thanks for the tip re layers with the wormer added Lord Flynn, it will simplify things in future.