The reality is that HMG are already softening what is, as Michael O'Leary said yesterday, a totally unworkable system since we don't have a UK equivalent of the STASI following people's movements, and the regular police simply don't have the manpower to go knocking on doors, let alone forcing entry without a search warrant to check who is, or isn't at home.
The police would not need to enter homes at all. It would be down to the individual to come to the front door with their passport. No one is going to hide inside a home if that is where they are meant to be so have committed no crime. Fines could be imposed for those that did not identify themselves. If they were a foreigner a marker could be put against them to ban their re-entry. The threat of house calls would make many comply.