I have no idea whether they actually verified my hours with the school or not, but I simply noted the contact details in the comments column of my logbook, and attached a note when I sent off my PPL application. If you were to get the school to stamp your logbook and note the FI's license number that makes it even easier should the CAA choose to verify the hours.
If you want it in black and white, give flight crew licensing a bell at Gatwick. They're usually quite helpful.