Hi Nav420
Derek at Bournemouth is very good, with many years in 'the trade'. From what I've heard, you shouldn't go far wrong there. (His partner Claire does the groundschool though).
From knowing Derek in the past, what I can tell you is his mantra - 'if you want to fly in the UK, learn in the UK.'
I personally can't see anything wrong with learning in the US, but if I was in your situation, I think I'd stick to the UK to finish it off.
The weather here, unfortunately, is part and parcel of flying in the UK, but I can understand your frustration. If I were you, I'd get the last two exams out of the way, then re-evaluate.
Good luck