I'm in Canada but I have experience in installing cable TV,Satellite TV and Antenna wiring.
My first question is, is the dish or antenna on the roof ?
Can the cable entry point be at a height where they would need an extension ladder or a pogo stick to reach the cables?
Are you capable of running the coax cable to the various points through out the house yourself(is this permissible in the UK)?
It sounds like they are not just vandalizing for the sake of vandalism....but they are removing sections of wire so that they can re-sell it for the copper wire value (which is at an all time high right now). Here in Canada there are stories of vandals and thieves breaking into electrical sub-stations and actually cutting out and removing electrical wiring from transformers....while its still live !
I did all the wiring for my cableTV,Satellite and antenna wiring in my own house.The only exposed wire is way up at roof height and the cable enters the house under the eavestrough making it way out of reach of vandals etc.
Hope you can get you TV systems up and running soon ......with the wiring out of sight !