If you get your car MOT'd more than one calendar month before the due date, then the MOT would have to start from that date. For the rest of it's life it will be MOT'd three months early (unless at sometime it has a second MOT before the previous one expires, or someone SORN's it). As said elsewhere on this forum, dealers like to get MOT's done when it suits them, so as not to have everyone bringing their 3 year old car in for an MOT for the 1st of September (or March). I would get your MOT and service done when you return from holiday, that way the MOT will run from its 3rd anniversary.