We use Gagens nr. Wisbech for our slaughter - never had them butcher it for us so can't report on that (apart from making a sausage mountain from the cull sows). They are always helpful enough and decent with the unloading. Actually, thinking about it, I almost go past your place on the way, might be possible to sort something out if dates align favourably?
Re: wormers etc. our farm animals are with Isle Vets at Ely and they have helped organise sharing bottles amongst a few of their smaller clients. I'd be interested in this though if others are? As a starter, I need to heptvac our sheep (12) and will do the nanny goats (4) aswell in a couple of weeks, so if anyone wants the other half of the bottle?