Hi there ! It's great that you took some time out before starting university , sometimes a little break is exactly what you need before you start a new phase in your life.
Assuming that most other universities will operate the same as ours in regards to societies , you should be able to tryout , join and leave societies as you wish at any time of the year , at DMU you can easily join online. You may have missed some fun gatherings or events by the time you join but that should be about it , you will probably be amongst many students who start in January and join societies a little later.
Starting in January is pretty much the same as starting in September except that it is colder and you won't have a freshers week with all the fun events but student unions host events all throughout the year and you will still have plenty of opportunities to socialize.
Just be aware that in student halls some students may have already made friends and you will have to play catch up in that aspect but luckily for you there will be plenty of students in the same boat as you.
I hope this helps and enjoy your break before university starts in January 😁
Cece ✨
Energy Engineering Student
De Montfort University