You do need an hour with an instructor as well, unless you've already done that within the second year of your two year cycle.
I'm not local, but what about Caernarfon? IIRC there's a school there who can do your flight if required, and should have an examiner on staff? That would be what, about a 75 minute drive from Aberystwyth?
Sending your logbook to Gatwick's not an option, but if you have the 12 hours including 1 with an instructor, then posting to a friendly examiner is (or if I were you, posting the licence with a photocopy of your logbook - you can get a new licence printed, but a logbook's rather tougher).
Or if you've already done the instructional flight, check if your instructor has had experience examiner privileges added to their licence (a recent innovation) - in which case, arrange to post it to them.
G