If the entire Britain wasn't so completely H&S focused, I'd tell the planning team to tour Denmark one summer, and do the obstacle courses in Fårup, Sommerland Syd and Djurs Sommerland. Then put up something similiar. Cheap, requires no space whatsoever, unique and suitable for all ages.
Too bad one child in a million is doomed to fall down somewhere, and, unlike Denmark, the parents won't give the kid a pat on his back, buy him an ice cream and be a bit more quiet the rest of the day. They'll phone The Sun with one hand and their lawyer with the other, and the park will be the ones in trouble.
However, if you feel that I am overreacting, which, considering the fact that I don't live in England and haven't experienced the system myself, is quite likely, an obstacle course is recommended. Any playground manufacturer would be over-happy to get a "big" contract with a park, and any kid will love to be allowed to climb in the funny structures at a park without the risk of being overrun by a coaster cart.