Anyway my lazy question is what is the easiest way for me to now get the standalone FAA certificate given that I am based in the UK?
I'm pretty sure the easiest way is to go to the US and do the standalone PPL written and flight test there. You are also going to need a sign-off from the CFI that you're ready for the exam, and it may actually take a few training flights before the CFI would be happy to sign you off. After all, there are some skills required for the FAA PPL that are not part of the JAA syllabus.
Furthermore, you'll most likely need TSA clearance and an M-1 visa.
It should be possible to do the written exam in Farnborough, and it *might* be possible to do the flight test somewhere outside the US. But that will not release you from the TSA requirement (which applies to foreign FAA flight schools too), only from the M-1 visa requirement.