~~
need more info, eg command on +30 tonne aircraft?
If not.
medical to be done at Gatwick ~200 GBP
14 JAR exams ~ 55 GBP each.
Theory. You need to do some but not all, the thing is, what do you cut out?
Full time (I used to recommend ATA but they're not accepting new students. 650 hours ~ 6+ months) ~3-4000 GBP
Distance Learning (see Bristol Ground School for that) ~2000 GBP I think. 2 x 2 week intensive brush ups.
Flying.
If he has +500 hours on a multi pilot a/c, sim to get up to speed and then a sim check with the CAA observing. Budget ~400 GBP/hr and ~700 for the CAA examiner.
If not, a min of 15 hours sim/aircraft time to convert the IR (+CAA examiner)
Add more money for the MCC if not got 500 hours multi pilot/crew time.
Add even more money for a type rating... If not got +500 hours on an ATR/737/A320 etc...
It's costly,
good luck