Well, water cannons would be useful right now.
What really baffles me is why the police seem unable to act against them. E.g. the ones sitting on top of the caravan under the arch.
Why not simply couple up the caravan and tow it away? Give them warning and then if they don't get down and they fall off it is their fault. Treat the ones who glue themselves to things in the same way. Give them some solvent, move the car or whatever and leave them and their mates to it. There are laws about highways, protecting other people's property, public indecency (if they glue their behinds to things) etc..
In other words, there are ways of inconveniencing them as much as they inconvenience us, it's just that the political will is lacking.