Monkey,
I did my PPL with Leading Edge just over 3 years ago now and I couldn't recommend a better place to train. Very professional instructors!
With regards to availability, there are always plenty of instructors and aircraft to fly even at short notice. Obviously there are the usual problems with aircraft maintenance etc. They have an online booking system so you book an aircraft when you want with who you want.
I think it's very important that you try and stay with the same instructor throughout your entire training and Leading Edge will do all that they can to ensure that this is the case.
The Ops staff are very accommodating. You should give them a call or pop up to the club for a chat, everyone is very friendly! Hope you've had a look at their website.
Al