Welcome to PPRuNe as a poster!
Similar answer to one I posted yesterday to another question; the information you need can be found in
LASORS 2004 (warning 4.7Mb download!)
Section C5 (page 122) covers Licence Reissue, including Expired Licences.
If the holder of a UK National or JAR-FCL pilot’s
licence has not held a valid Certificate of Test,
Certificate of Experience or Certificate of
Revalidation for any type/class rating that has
expired by more than 5 years** they may not have
their licence re-issued until such time as an
appropriate valid medical certificate and Certificate
of Revalidation are obtained. Applicants may either
renew an existing rating within their UK or JAR-FCL
licence or may wish to transfer a type/class rating
that he/she is currently flying under the privileges of
their non-UK ICAO licence.
Detail as to what needs to be achieved to obtain Certificate of Revalidation is in Section F (page 246 onwards), varies by type, and made my brain hurt!
RC