I did my PPL at Headcorn last year and was most satisfied with the training. There's a large, stable team of self-employed instructors with their own businesses at Headcorn, each registered as a FTO.
It's not hard to get to from North Kent (it is North Kent!), takes less than an hour on the train or by car.
Only downside is the grass runway. When it gets soggy, flying can be cancelled for a while.
Quite a large fleet of aircraft - C152, C172, PA28 and a stack of Robins. I did my training in the PA28, but would suggest you go for a Robin, as aircraft availability will be better. No landing fees unless you go somewhere else. Straightforward hourly rate, all included (brakes on/off).
Saying that, I never had (have) any problem getting the PA28. It was more difficult getting my instructor as he was getting busy.
I kept the same instructor from start to finish. As a customer of an individual's FTO, you'll get that by default and if you aren't happy with the instructor you're with, with so many self employed others there, it won't be hard to change.
http://www.headcornaerodrome.co.uk
or 01622 891539
The instructors all have links from the aerodrome's web page.