I kind of agree with the points people are making that go against giving police guns, however we can't avoid the fact that the police here in the UK are woefully underequipped to deal with this sort of event, and also woefully undertrained. So I would actually advocate more weapons, but limit it to the police being given tear gas, stun guns and tazers, and rifles with rubber bullets. Nothing lethal, but enough to hurt and cause major pain to rioters, so that they are incapacitated and unable to cause harm to either police or the public. And yes, that should be standard issue to all police, because they don't know if they're going to be dealing with crazed psychos or simple muggers or what when they're called out, so the police need a way of dealing with the dangerous thugs properly without having to wait for firearms cops to turn up and without significant risk that the perp is going to end up dead.
Added to that, riot training needs to be improved, and fast, and every single police officer out there needs bto be fully trained and up-to-date on tactics to deal with this sort of thing so that rioters simply can't cause trouble to the extent they are now the next time something like this happens.