So I finally received a response.
Unfortunately it was written by the CAA ergo somewhat cryptic;
"Thank you for your email below.
EU European legislation (EASA) came into force on the 8th April 2012 which is going to change the pilot licensing rules and will affect the privileges of many existing licence holders. The UK CAA will not be issuing EASA licences until 17th September 2012. Applicants should be aware that the current Licensing guide LASORS will cease on 16th September 2012. For information regarding credits for training that had commenced prior to the 17th September 2012 please refer to CAP 804 Section 7, Part A, Page 7 ‘Article 9.’
Please refer to CAP804, Part I, Section 3, page 1 which states that ‘The CAA will only accept applications from pilots whose medical records are held in the UK.’"
Looks like CAP 804 is my next port of call. Though if anybody can clarify in the meantime whether or not I will need to transfer my Class 1 to a CAA Class 1 it'd be much appreciated!