Found the following:
(Edited to say the formatting below has got a bit messed up, but you can read the original at -
http://www.jaa.nl/section1/jars/435247.pdf
Appendix 1 to JAR-FCL 3.105
Validity of medical certificates
3
(See JAR-FCL 3.105)
...
If a licence holder allows his Medical Certificate to expire by more than five years, renewal shall
require an initial or extended, at AMS discretion, aeromedical examination, performed at an AMC which has
obtained his medical records. (EEG may be omitted unless clinically indicated.)
If a licence holder allows his Medical Certificate to expire by more than two years but less than five
years, renewal shall require the prescribed standard or extended examination to be performed at an AMC
which has obtained his medical file, or by an AME at the discretion of the AMs, subject to the records of
medical examinations for flight crew licences being made available to the medical examiners.
If a licence holder allows his certificate to expire by more than 90 days but less than two years,
renewal shall require the prescribed standard or extended examination to be performed at an AMC, or by an
AME at the discretion of the AMs.
If a licence holder allows his certificate to expire by less than 90 days, renewal shall be possible by
24 months.