We've got plenty of space before they go over land though, so can afford to escort them out whilst they're still over the sea if need be, or give them some time before taking further action.
Remember we routinely send up armed aircraft to do just that when the Russians start playing around on our air borders.
Turkey has had armed Russian aircraft crossing it's land borders on a regular basis for a while, and has consistently warned the aircraft before, during and then issued official protests afterwards.
After they shot down a Drone the other week you'd have assumed the Russians would have taken that as a serious warning, and started to be much more careful of where they were flying and listening to ATC and Guard frequencies for warnings.
I suspect if an armed Russian aircraft got over UK land without permission, especially after repeated warnings, and prior protests over similar situations going back months, the RAF may not waste much time in opening fire.
