piper999,
If your friend got their PPL in the late seventies or eighties, then they will have a non-expiring "lifetime" licence, so shouldn't need to do anything with that.
He will need a medical.
He doesn't need to take Airlaw or HPL, nor indeed any of the theory exams (except possibly Radio-telephony) Although after a lengthy time away, he way be wise to do some theory refresher work.
He will have to renew, rather than revalidate, what is now his SEP(L) class rating. This is done by undertaking refresher training as required, then having a LST. This is what he will have known as a GFT, but with the addition of a visual navigation sector. You could try having a read through CAA standards document 19 to get an idea of what's involved.
http://www.caa.co.uk/docs/33/Standar...19_A%20v6_.pdf
He will probably need to renew his FRTOL, see LASORS B1.5-6
Alternatively, there's also the NPPL to consider
NPPL Home Page