PPSC are no more. However some of the team who ran PPSC (amongst them, Roger Henshaw, David Webb and Pete Swatton), now run an organisation called GTS (Ground Training Services).
GTS uses manuals produced by a company called Click2PPSC, but are working on their own manuals (not sure when they will be ready).
Whatever, I have seen the manuals that they are currently using, and IMHO they are excellent. And the instructors at GTS are also very good indeed- some of the most respected in the business.
FYI, I didn't do my groundschool with them!