I see where you've got confused. I'll start again:
The UK CAA will validate (not convert) an FAA PPL - without the need for a flight test or exams. You need to demonstrate knowledge of Air Law and ATC procedures, but this can take the form of an exam OR a chat with an examiner.
This will result in an email from the CAA granting your FAA certificate the same privileges as an EASA licence.

This is obviously a better option as an FAA cert is cheaper, easier to maintain, gives automatic night priviliges etc; however if you actually want to convert and hold an EASA PPL, then yes - you will need to meet the requirements you refer to, including passing exams and a flight test.

But why would you want to do that?!

If you're intending living, working, and flying in EASAland, get an EASA licence. That way you won't be caught by law changes over your flying lifetime.
As your in Ireland, you don't have to worry about April 1 2019.

Yes I understand now rudestuff, thank you.
When I came back to the UK I did try to get answers from the CAA via phone and was told to email their licencing dept.for the answer to my question,6 months later I'm still waiting for a reply ! So in the meantime I wandered in to my local flight school/flying club and asked what I needed to do to legally fly in the UK as a FAA licence holder.
They couldn't give me an answer from their experience alone but were very helpful and offered to look into it. They came back with the EASA conversion route of a couple of exams for air law, human performance and a skills test ride.
Now looking at it, obviously it was assumed that I wanted to convert my FAA cert to EASA, I have now done the exams and due to do a mock skills test ride next week in readiness for a ride with the examiner, the prospect of the checkride doesn't daunt me unduly, but I would rather keep my FAA cert just the way it is so I think I will put it too them that there is an alternative option open by just getting the CAA validation on my FAA cert.

http://publicapps.caa.co.uk/modalapplication.aspx?appid=11&mode=detail&id=7863

That's the form - srg2140

Getting a full EASA licence doesn't affect your FAA licence.

Just your wallet.