i.e. the process whereby an examiner looks over your logbook, confirms that you have met the requirements and then signs the relevant bits of paper) must be completed within the 3 months prior to the expiry.
I've never done it that way. As soon as I meet the requirements, I get revalidated, which runs for a further 2 years from the ORIGINAL date of expiry.
I've noticed in the past with the CAA that often you can get a different interpretation out of them depending on who you speak to....a bit like a PC World "engineer"
(i.e. haven't got a clue what they're doing).