£13.57 Thats what we (freeride_trials) raised whilst doing a small event, NOT for charity either, no more than maybe 36m squared area on the prom. Basically, (after all the permissions were sorted out) we turned up, built a rig and then just chilled out all day riding it and talking to some people. I think its do-able, but I wouldn't travel to london for it. Thats why I think smaller, regional demo's would be better so that way people may be able to turn up to a couple if they wanted Also I doubt it would be that hard to get going because all you need to do is ask your council nicely if you can do it, ask if they'll provide the fences too (cos you definitly need them) and your away. The only real problem is sorting out things to ride lol