A few references :
JAR-FCL 1, Amendement 5 (the one currently in use by the UK CAA), Section 1, Subpart F (Class and type rating),
JAR–FCL 1.245 Type and class ratings – Validity, revalidation and
renewal,
(f) Expired Ratings
(1) If a type rating or multi-engine class rating has expired, the applicant shall meet any refresher training requirements as
determined by the Authority (which refers to the UK CAA) and complete a proficiency check [...]
The rating will be valid from the date of completion of the renewal requirements.
(2) If a single-pilot single-engine class rating has expired, the applicant shall complete the skill test [...]
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I assume you're looking to renew a single-engine class rating :
Fly with a CRE, have him sign your licence and send the paperwork to Gatwick and you're done...
Only thing you might want him to check is which form is to be filled and sent, that's where you want to call Gatwick (and not Paris, but I think I've said it already
).
Might be this one :
http://www.caa.co.uk/docs/33/SRG1119.pdf