You can hold a PPL without the FRTOL but without the FRTOL you will be unable to use the aircraft radios to communicate as you will be un radio licenced.
You can take a skills test either before or after the FRTOL, however if you apply for the PPL and FRTOL separately I.e. in different envelopes you will pay 2 fees.
The PPL Skills test pass is valid for 6 months for licence issue so my advice is to crack on with the FRTOL exam soonest and send both forms together. It will save time and money!
Hope the above helps - its all in LASORS.
Regards, D.