So how does one get properly good at dirt-jumping then?

oops

here’s one for sale. I’ve got it and it’s very good. 😀

It takes you from basics to more advanced techniques from a DJ legend

http://www.ebay.co.uk/itm/Kona-Mountain-Bike-DVD-Dirt-Jump-John-Cowan-/320845437724?pt=UK_CDsDVDs_DVDs_DVDs_GL&hash=item4ab3e0db1c

Chicksands has loads of stuff, and not far north of you.

You need a SS dirt jumper frame along with the stiffest forks you can find.

Trainer jumps/packs:

Bigger jumps/packs:

May I stick my neck out and say that spd’s are likely to make your technique rubbish. Get rid….
Woburn is amazing for jumping, however, its not so great to begin on but it is constantly morphing so something do-able may come up.

Muddy Ground

Try the foam pit at a place like Skaterham in Caterham…..

Although skate parks are intimidating enough at the best of times, and turning up on a mountain bike (faux pas #1) as a complete beginner (#2) and hogging the foam pit (#3) is probably not going to win you any friends.

You’ve correctly identified that big MTB-style jumps are a different kettle of fish, but they’re not THAT different. If you’re comfortable in the air that’s the number 1 thing. The main difference is that proper trails kick you upwards more forcefully so you’ve got to be more fluid. As said, you need to ditch the SPDs, and getting a jump-specific hardtail is going to make things way easier than a bodged XC bike. The main issue I found (which is why I suck at dirt jumps) is that you need the balls to actually hit the jumps. I think because trails are typically slower, you can bottle it more easily than you can big jumps as part of a DH course, for example.

I also wouldn’t say that being able to ride BMX-style trails makes you a ‘better’ rider – I’ve been riding with people who are ace at trails but can’t really ride fast MTB tables. It’s a different skill, it’s not about one being better.