Welcome to PPRuNe and the Private Flying forum! You've had lots of good advice already, but I may as well stick in my twopennorth too...
If you live in the South-East, flying over to France for lunch is one of the benefits! I'm jealous; from North Wales it's a bit of a long haul. Seriously, many of the pilots I know in the South of the country do it all the time. It only seems like a big deal now; soon it won't. I would get your medical out of the way before you start, and if you can pass it, go for the JAR PPL. If not, then it's nice to have the option of the NPPL. But if you're normally healthy, the medical is not a problem.
As to schools and instructors, visit a few and see what you think of them. People vary, and what suits one may not suit another. Ask if you're likely to have the same instructor for most of the course, as some sort of continuity really helps. Ask not only what they charge, but how they charge - as someone pointed out, paying home landing fees can add a lot, so can whether they charge from engine start, or brakes off, for instance. If you learn at a large airport, you could spend a lot of time hanging about waiting for other traffic; on the other hand, you'll learn how to cope in a crowded environment. At a smaller place you'll waste less time, and learn to make your own decisions without ATC helping out, but may find flying to somewhere larger a bit daunting for a little while.
I hope I'm not onfusing you, but as one of those who just wandered into my local flying school without doing any research at all, I wish I'd had this sort of advice when I started.
Above all, ENJOY! That's an order!!!!!!!!!!!