Hi there,
I'll try to be as helpful as I can, I hope it doesn't get too chaotic as my writing normally does this late in the day.
I trained at Stapleford for PPL and then the IMC rating (now called IR(R)). I also flew from North Weald for about a year. Both places are commutable from London - Central line takes you to Theydon Bois or Epping, respectively, and from there you can get a cab. +£20 to each lesson I know, but at least relatively reliable and not too time-consuming.
Stapleford are a big commercially oriented school and it is vital to find an instructor who (a) you get on well with, (b) understands and accommodates your non-commercial aspiration and (c) can book lessons infrequently. If you end up going there, I have one in mind whom I could recommend, PM me.
North Weald Flying Group is not surprisingly a large group at North Weald
and the majority of members are PPLs who fly their 7 aircraft, booking as they go. The Group is an ATO, however, and has two instructors; might be worth giving it a go if you look for a more relaxed environment to learn in. I was a member for over a year and flew the Archer and the C172s.
First and foremost,
visit all the places you consider, and compare the general feel and atmosphere. Only then it may be worth looking for opinions of former students from the few particular schools you'll like. Don't be put off by occasional chaos or being ignored at Stapleford - most of your training will be spent with an instructor in the cockpit, and not with the admin people at the reception.
Facilities are important, but you can assume that any authorised ATO maintains their fleet in decent shape, unless you hear on the contrary from someone. ATOs run on thin margins, so you can imagine that mechanical soundness of aircraft will take priority over the looks of the interior. Stapleford trainers look awful, NWFG aircraft look much better, but not like factory-new either. All of them flyable, maintained to public transport standards and handle well.
When training, I flew rather irregularly, sometimes once a fortnight, sometimes pressing for a few lessons a week, with two 6-week breaks due weather and one 4-month break due to a "do I really want it" moment.
Hope that helps!
/h88