You're going to have many difficulties , first off you're RPL is not an ICAO recognised licence. Schools in the UK may give you a reduction in the hours required to obtain a PPL, up to the discretion of the ATO, (training organisation).
Second, with no ICAO recognised licence ,you will need to complete the 7 PPL subjects, not the ICAO licence conversation exam.
You will need to obtain a UK class 2 medical, regardless of you're CASA class 2 .
You will need a new English language assessment .
In effect your starting all over again.