It depends on which branch you're going for, however off the top of my head I know that Chef has a significantly shorter wait time at the moment, and Warfare Specialist has a waiting time of roughly 2 to 2.5 years waiting time.
If you are a trained rate, rejoining your former branch with a break in service of less than 5 years, once you pass selection, you'll usually join on the first wednesday of the month, a month or two after gaining SC. You join Raleigh, RNFT, APWT, RNST, respirator checks, kit issue, weekenders, Sea Survival, PJTs & straight to sea.
If you join as a trainee, you wait about two or three months longer to gain approval to process & full SC, and are then allocated an entry date the same as any other new entry. Places are allocated anything between 3-9 months ahead of the start date. As stated above, the critical factor is the branch you are joining - the longer the wait to join, the longer the notice given.
In which case it depends how many MW courses are running, but I think we're underborne, so all you're waiting for is some chimp to bang-out of Initial Naval Training, creating a place on the phase two bit. When they do, you'll probably join Raleigh, RNFT, APWT, RNST, respirator checks, kit issue, weekenders, then jointhe class, just after they pass out from Raleigh and commence phase two. My guess is you'll get maybe six weeks notice to join but it depends how often there are intakes of MWs - it maybe only once a term as it's a small branch.
Reading a recent enough post about this it's a bar from entry!
It would almost definitely require another medical as muskovardo said above and be a fail, thanks for your time, enjoy the rest of your life.
Type into Google ' Bootneck Blueprint'. It's a website run by an ex-Royal Marine who is now a personal trainer. On there he has a 2 week intense workout course to get you back up to standard, and as it's for RM it'll get you ready for RN no problem. I believe it's £5 or there abouts, and you can get it sent to your phone/tablet/ipad/computer. OR you could run 3-5 miles a day 5-6 days a week, and do the RN/RM fitness programme found on the RN website. Or if you're able to get a personal trainer a few times a week that'd be good too, similarily a bootcamp can be found sometimes in nearby parks/gyms, and I've found they're pretty good to get your CV/body weight exercises better, faster. Tabatta training is also good, I understand it to be 30-60 seconds of max effort push ups for example, followed by 30-60 seconds of max effort sit ups, etc etc. Do that for 10-15 minutes a day coupled with a 3 mile run minimum each day and you'll be killing it at PRNC mate.
There's a lot of ways to get fit mate, and if you have the time that's even better as there's no excuse not to train unless you want to fail Phase One! I've recently started training again after taking a stupid couple of months break from it and it's horrible mate - 5 minutes slower on my 4 mile run! FIVE!!! It's shocking! Obviously best to stay in shape and not be a gimp and stop training, but as stated above there are various ways of getting fitter quicker. Plus the extra fear will motivate you not to suck