Are the hives close to the neighbour's boundary? He/she may be thinking you will expand, and at some point start devaluing his land, and/or your bees may 'be a nuisance'. Having them some distance away may mollify him. Having a high hedge between you will help (but if he get horses and they eat your hedge that won't help relations... experience speaks here). If s/he plans to get horses in the future the bees might be bothering him. There are rumours that a few bee stings can kill a horse. That's not, technically anyway, your problem, because they will be unlikely to be able to prove without doubt that it was your bees that caused any such grief.
In the end bees are pets or livestock, and you can keep livestock (but not pets) where you like till they are ruled to be a nuisance by a court. That's my understanding anyway. So it may, incidentally, be a bit of a hobby, but actually they are feeding you/providing you with produce, and that's allowed anywhere it isn't specifically outlawed (like new smelly livestock building aren't allowed near houses). The number doesn't matter - that's just the enforcement officer trying to get rid of the problem quickly.
The BBKA might be able to advise: taking out an insurance policy with the NFU might also get you some legal advice. Full-on legal advice will probably be expensive.
As to where to go: mostly wait and see, and don't let it bother you.