but do hold a UK PPL (A) with a SEP rating.
First question, is it an EASA licence or just a UK licence? As it was only issued 2 years ago it should be an EASA licence.
If you have the experience and the hour with an FI then all you need is a UK Examiner to sign the licence. A revalidation by experience cannot be signed by an Examiner whose licence was issued by another State, similarly a FI with 945 privileges can only sign the rating if they conducted the last flight of the one hours dual experience and they also have a licence issued by the same State.
It must be revalidated before the expiry date or you will be into a renewal.
You can always send the documednts to an Examiner for signing. There should not be any fee associated with this. You can send it to Gatwick but they will charge and take ages.