Your local beekeepers may well be an excellent source of well bred bees, but equally they may just want to pass on splits from their swarmiest colonies late in the season when it's too late for them to make surplus honey. Some groups also pass on swarms for little or nothing, which can be great or not, a bit of a lottery really.
There is a lot of nonsense preached about local bees, as if local is a guarantee of quality. Your local bees are as good as your local beekeepers, who provide the main selection pressure on the local gene pool, whether they realise it or not. Join the local group and see how well run and helpful they are - I think it's a good guide to how good their bees will be.
If in doubt there is a good professional nuc supplier near Banbury who you can easily find via google. It will cost you more though, but a good nuc in May is likely to give you a super of honey the same season.
My only other recommendation is get 2 hives - maybe even hedging your bets by sourcing 1 nuc professionally and the other from the local BKA. That will be an interesting comparison, but the main reason for doubling up is that a colony can save another colony if you are unlucky enough to go queenless for any reason, which will happen sooner or later in your beekeeping career.
Good luck.