just wanted to ask because it is cheaper than paintball because you can re use the balls. also is there places in london that facilitate this type of event
its commonly called reball and its main use is as a training aid for tournament teams, although there is one indoor site i know of that uses them in scenario style games.
can't remember the name of it sorry bud. there was a bit of a rant about it a few months back on here but i'm sure somebody else will have a better memory than me.