The info I got from my AME in the UK is that renewal and revalidation need the same medical examination - certainly in the short term. If you left it some years, you might have a problem.
The UK CAA website info shows the same requirements for revalidation and for renewal.
See this:
Revalidation and Renewal of JAR Medical Certificates | Medical | Safety Regulation
It should (!) be the same throughout JAR land. Good luck!