Think carefully before joining (UOTC)
Pros
Physically demanding - good workout, keeps you fit. Get paid (although not very much). Met a few really decent people who I'm still friends with. Can do some fun stuff like skydiving that you might not normally get to do. No commitment to continue with training after completion. For me ultimately, it was very useful to learn the sort of thing that I didn't want to do with my life.
Cons
The positive reviews on here I can guarantee are not representative - about 60-70% of people I signed up with dropped out in the first year. Big time commitment, interferes significantly with your studies though obviously you can make it work. Very much geared towards people who were in the cadets or (in some cases) the TA/daddy was Major-general and/or very firmly set on entering the military (doing degrees I didn't even know existed like 'War Studies'). If you are not part of one of these three groups, don't even bother joining - you'll be way behind and constantly made to feel like an idiot. Insular, very right wing, bullying, borderline racist/colonial attitudes and a lot of stereotypical RAH types. It seems for certain people they viewed the UOTC as a 'safe space' to say things they wouldn't normally say in civilian life. A handful of the instructors - not the actual army officers who were professional, just the cadets who were a year or two ahead of us - clearly enjoyed abusing their position and generally thought they were the Sergeant from Full Metal Jacket.