NagsTeeth,
It's not so simple as 'How do I go from PPL to ATPL'.
Once you get the PPL (Don't know why you want it), you must get a CPL. Then the hours required by CAA/JAA for ATPL + IR and experience in Multi.....etc....etc.....
This not something that you can purchase. It will take many years.
There is no school in the world that can give you
PPL to ATPL in one course. If they say they can, they are full of SH!T
After saying that, if you still want to continue, then my advice is, if you are still in your 20's, join the RAF/RN and get it for free.
Cheers,
OffshoreIgor