We find a big stadium somewhere that isn't being used or, worse case scenario, we build one.
Then we take all the rioters - the EDL (English Defence League) types and the MDL (Muslim Defence League) types (basically anyone who has been caught on camera setting fire to things, punching innocent bystanders, throwing rocks at the police etc) and put them in the stadium. We can also advertise it so people that want to fight can go there voluntarily. We put some nice things for them to play with in - a few old cars to set on fire, maybe some bins, etc. And just let them... fight it out away from everyone else? And then everyone else can get on with their summer in peace.
Best case scenario, they all either kill each other off or realise the error of their ways and that peace is the best option. Worst case scenario is they somehow bridge their differences and band together as one super-mob but we cross that bridge when we come to it.
I was going to suggest televising it but that would actually be a bit barbaric so I would rather just let them get on with it in peace. Its not cruel. These are people who want to fight and smash things. I just think they should do it somewhere contained.