ciderman,
See
http://www.caa.co.uk/docs/49/SRG_MED...ateExpiryDates[2362].pdf where the changes are summarised. Basically, it's every year up to 60, EXCEPT for those pilots involved in AOC type passenger carrying single pilot ops. So if you're an instructor or multicrew, it's annually.
However, not all AMEs know this, or didn't when I renewed mine last month. Not that it matters - you'll get the same certificate, stating that the validity period varies depending on what you do.
Hope that helps.