AerBabe, that is nonsense. The NPPL is not "designed for medical conditions"!
An extra 13-14 hours should be about right - your RAF scholarship training will stand you in good stead as you'll have done most of the basics. You should just need to get back up to speed with GH, then do the navigation element before the NST, Q X-C and GST.
Whereas a JAR-FCL PPL would be a minimum of another 25 hours on top of the 20 hours you already have...
(25-14) x £100 ph = £1100. For those who think that's an insignificant sum, well, you could always send Big Cheese 1 the odd £1100, I guess.
He can always upgrade his NPPL to JAR-FCL PPL at a later date - and with a licence he can legally cost share with his passengers, so can potentially fly at lower cost than would otherise be the case when he first gets his licence.