Hi Sam,
If I were you - I would look at the nearest 2/3 (or more) airfields to you online, see the flying schools / flying clubs around, and book a trial lesson with each one of them.
I would then find the environment that I learn best in, some people learn best in schools, with rigid 1 hour slots etc... whilst others (like me) learn better in a more relaxed environment (club), where a cup of tea with the instructor after the flight for a debrief is a prerequisite! Of course schools vary wildly, as do clubs. Prices in the UK aren't too far apart, but there are always a few that are more expensive than others. As this is generally very much a personal experience, and the relationship you had with the instructor and other club members / other staff, it is very hard to give you a definite "best school".
There are a few pointers on how you are being charged though:
1. How is the flight time charged? Tacho, Block, Hobbs?
[if you don't know - generally you'd do around 0.8 tacho per real block hour and is measured by the engine tachometer, block means from brakes off, to brakes on, hobbs vary from oil pressure switches to wind switches activated over a certain threshold]
2. Do they add any taxi time on these?
3. Is there a "fuel surcharge"?
4. Do they charge extra for ground school or is this taught along with the brief and debriefs in addition to self-study?
5. How much do landing fees cost at that airport?
6. How much a touch and go / circuit cost?
7. Is there a membership you need to pay for on joining?
8. Never pay everything up-front!!!
I've been bitten a few times by not understanding the way I was being charged, I once paid just over £250 for 1 hour in a PA28 (from 1977 - not even a new one!) because I didn't understand the payment structure (and they clearly ripped me off - as other places often were around the £150 - £180 mark dual).
Cost is important - but remember that it is also the level of instruction, and the particular instructor you've managed to secure.
I wouldn't waste my time going abroad for it, the savings are quickly no longer savings when you add accommodation, transport and the training you'll require upon coming back to the UK. (I did the maths some time ago, and you barely save enough to warrant the move).
Let us know how you get on!
Best Wishes,
A