@Happleandhorange I'm not gonna lie, I was hoping you'd try BodyCombat! One thing we always suggest (and hardly anybody does) is to just do 4 or 5 tracks and then go off for a wee stretch. Then you can add another track as you feel like it, until you're doing the whole class. It's not good to train so hard you're completely wiped, but it's easy to get caught up in the class and we all do it!
Another thing I suggest is to take all the lower impact options offered, and don't feel like you need to keep up with the instructor or the front row champs. So you don't need to do full range lunges and squats - or all of them (cheating and resting is completely fine), all your kicks can be to knee height, and when the dreaded running knees come, you can march in place instead of going Full Spaniel.
I really hope you just enjoy the class, and don't worry about the moves either, you can work on one thing at a time.
BodyCombat is one of those classes that people love and go to for years, so there will be people in there that are just amazingly fit and can do all the moves.
Sorry I do go on, this has been my Ted Talk about BodyCombat, thanks for reading!