Taking a gap year after graduating?

join the ski club at uni perhaps?

And of course you can take a year out whenever you want in the future.

Taking a year away from medicine, after med school, is possible. It is not easy to organise something officially during a postgraduate training scheme (e.g. during Foundation training or during specialty training) and would usually need to be time spent doing medicine abroad, or doing research. Time spent abroad doing medicine is unlikely to be counted towards your overall training, particularly if it is in a developing country (and having time abroad accredited towards your overall training is very difficult to organise). Many people choose to do it between two training schemes, e.g. between FY2 and CT1 -this is what I did, I am spending a few years doing medicine in Africa, which will not be counted towards any of my UK training.

I'm assuming that post FY2 is my best bet?

You'd have some problems trying to convince the Important People that a ski season should count towards your postgrad medical training ;-)

Doing something not-medical after FY2 could incur its own difficulties. As in, at CT1 interviews you'll be expected to present portfolios and evidence of ongoing professional development, and I think you'd have problems convincing them that you were keeping your skills up to date, particularly alongside fellow candidates who have current, up to date portfolios etc etc. Things may well have completely changed by the time you get there, but currently competition for CT1 posts is generally quite strong. For example I am still (trying) to keep a portfolio and logs whilst I'm here in Africa. Definitely worth seeking some advice from your Deanery nearer the time though if you want to take a year away from medicine. It's not impossible, but they will be able to best advise in terms of things you should be doing at the same time to show CPD / keep up your skills etc.

Definitely.

I didn't know if I could work as a locum for the rest of the year, a ski season is only 5 months long.

I know it would put me at a disadvantage career wise but I want to live my life, I don't want to live to work. There's things in life on my bucket list and I want to tick them off . I'm not fussed about being the top of my game, yes I'm ambitious but I want to take every opportunity that I can. It would probably be a year away from medicine completely, I'd like to spend the rest of the year travelling so I wouldn't rule out doing something medicine related for that time though. Particularly in another country.

I honestly think I'd have life long regrets if all I did from this point on is work the the UK for 50 years with the odd holiday once or twice a year.

I'd say go for it, just make sure you do what you need to do to tick the right boxes. It's a long way off for you anyway - the application process may have changed completely.