The ATPL at London are the ATPL theory, you need a PPL to take these exams, all 14 of them.
An integrated course can start you from scratch: EG zero experience, but if you want to do just the ATPLs at London that would involve the modular route.
As said above, class 1 medical before anything, make sure your body is up to the job prior to throwing piles of hard earned at the training schools!!
Will take 1 Year approx full time, but if like me you opt for the modular route it takes as long as it takes, the more time you put in the quicker you will finish.
I think three years is the average for modular part time? I saw it somewhere but do not know where?
Whatever you decide, look into what you want to do allot more so you can make informed decisions, and DO NOT PAY FOR ANYTHING UP FRONT!