It would be very realistic to get a ppl in 2/3 months
If u looked around u could probably find a 3 or 4 week ppl course run in the USA for about £2500 including accommodation. If u got a cheap ticket there and dont spend too much u could probably come back with a ppl having spent less than £3000. I think lots of these courses are British run schools so u wouldnt have to convert ur license or anything(although i might be wrong)
If u chose to do it in Britain then u could probably do it for less than £4000 because there are quite a few places that offer cessna 150/152s at under £70 an hour but remember u have to add on other stuff like ground tuition costs(but some places do that free) and the cost of a medical but like i said u will probably be able to do it for less than £4000 and if ull be flying in the UK then this might be better as ud be more used to the weather and stuff
Something id recommend u try to get would be a magazine called "Learn to Fly Guide" which is a magazine produced by Flyer magazine once a year. It has a very useful listing of every flying school in the uk and tells u how much course and hourly rates are at each.
It will show u what the cheapest airfield near u is and also contains advertisements for several ppl course in America.
Hope ive been of some help