I stopped riding MTB’s shortly after the third Malvern Hills Classic, the one where someone ended up getting stabbed (to death, I can’t remember). I rode street, park and flatland BMX. My biggest discovery was that it is unbelievably hard. Most BMX takes huge amounts of guts, the ability to take pain on a regular basis and practice practice practice.
Riding trails (not singletrack, those huuuuge jumps dug out in sets) is amazing and possibly the safest, practice small and work your way up. Again guts are required as those doubles have no middle. 🙂
Street riding is probably the most accessible and will teach you loads of good tecnique for that technical singletrack. I can bunnyhop a flat pedal MTB after years (I was a slow learner) of street riding. It is a bit harsh on bikes but all bikes are a lot better now and parts are über cheap compared to MTB’s. If you live in a city it’s something you MUST do.
Skatepark riding is what most people do as well as the above, as it’s generally indoors so an all year round thing. Good place to learn and there WILL be someone worse than you there. Learn the etiquette of skateparks first and you’ll be fine. There are some free outdoor skateparks around, certainly more than when I started.
Flatland is fun to mess around with and all the top riders have some flatland skills. However it is by far and away the hardest discipline you can do. And I’m comparing it with ANY form of cycling. Top pro flatlanders have ridden nothing else for 10+ years, 6/7 hours a day. It really is that hard but the kick from pulling stuff is amazing, I know.
Racing is good too, but not as fun and you can always ride most tracks anyway.
As far as a bike goes, spending £300 on a new one is the best idea. Second hand ones may have all sorts of stuff on them which isn’t suitable for you, could have easily led a hard life and may also put you off in the end. Stick with one of the big brands, get 3 piece cranks and 14mm axles and a cromo frame and you can’t go too wrong. It’s the same as us telling someone to buy a £400 specialized.
Email me if you want any other ideas.
Phew! (typed on phone!!)