Using an FAA CFI for FAA PPL which is perfectly legal to use in the Uk with NO conversion (and includes night flying):
Per hour
Aeroplane (C172 or PA28) $70
Instructor $35
Examiner $400
Ground exam $90
Say 55 hours: $6365 which today =<£3500
Flight: £350
Hotel: £645 for 30 days
Grand total to do it in America in 55 hours:
£4495 and guaranteed in 30 days