Go back to the school where the examiner is based, talk to the Head of training along with the examiner and explain the predicament.
If sense prevails and the ATO knows you and your experience they will probably sign you off as no further training is required, then you can take the LPC after the examiner follows the process laid out in IN-2015/050
http://www.caa.co.uk/docs/33/Informa...ice2015050.pdf
Assuming you pass all he needs to do is send of the Test report in accordance with the instructions he gets from the CAA and re-sign your ratings page with the test date etc.
When you are ready send everything off to get an EASA licence.
No need to make a drama of it, just resolve it.
And for the future, if getting a CAA authorised examiner to do your revalidation by experience is not practical, instead of doing the hour with the instructor, go back to your examiner who by now will know the procedure and do the LPC. That way you don't even need to knock up the 12 hours as well.
Its less hassle than changing your State of licence issue. To be honest, the UK CAA are the best regarding medicals and more likely to be constructive that other states. I have got someone through the issues with diabetes and the CAA bless them are really having to battle in EASA land to prove that diabetics can be safe pilots.