You should take note that money, while an important factor, should not be a decisive one when it comes to whether you should or not start reenacting. Yes, stuff is expensive, but for the most part (at least in my own personal experience), as long as you show interest and are friendly to the unit you want to be with, they'll lend you enough gear to get you started.
Granted, you'll have to buy the basics (pants, shirts, maybe gaiters, shoes, etc), but the "harder" things can be bought later. Things like coats, shakos, cross straps, haversacks and canteens are almost always available in most groups.
The musket part isn't that hard, either. Idk how are things done in the UK, but in Waterloo 2015 I saw several units storing a decent amount of "fake" muskets, which were distributed among those who didnt have a real gun. Perhaps some of the groups there follow that same trend, and have one of those available for you.