The son of a friend (in his mid 30s) went on holiday to Malta with his partner. They returned to 14 days quarantine and that lasted three days before they went off on another holiday to Cornwall. No doubt if he had received a call on his mobile checking he was maintaining quarantine he would have lied and I doubt the location of a mobile can be traced without a warrant.
So is this a rant against the irresponsibility of his generation? No, although the fact that many are irresponsible in this context is well established, it's to illustrate that 14 days quarantine simply doesn't achieve its aim and should be replaced by a test upon arrival back in UK and another test, say, five days later. If both are negative normal life could be resumed. There would certainly be much more likelihood of adherence to 5 days quarantine than 14 days.