The latest edition of UK CAA's Lasors is still dated 2008, and my (incomplete) search there found nothing that addresses this issue. They seem to assume that most people are on JAR licences these days.
My suspicion is that you will find that only a UK-approved examiner can do this job for a UK national licence. For a definitive answer, I suggest you e-mail the CAA at
[email protected]
Good luck! My experience is that they are normally very helpful.