When I lived in Camberwell, rats used to be regular visitors, entering the house via the toilet and sometimes sitting in the airlock on the U-bend, with their tails visible in the pan.
At the moment, there is a rat in the bedroom, here in middle clas suburban Barnet. I can't find it anywhere; I went to B&Q yesterday and bought a humane trap which I've baited with fudge (they say Galaxy chocolate is best so I'll try that if the fudge doesn't work). It's been there for two days; every so often I can hear it rustling. the cats and the dog are not interested; so long as food is in their bowls and they have a radiator to snore next to, they're not bothered. I chased it round the kitchen two days ago trying to catch it in a bowl, but it's a bit unnerving. A rat bit me on the finger once when I was rescuing it from a cat, and I had to go to get a tetanus jab. The bite bloody hurt, and I've got a few gigs coming up and guitarists don't need gnawed fingers.
I'm going out this morning, it's horrible being indoors fighting a battle of wills with a tiny and unhygienic rodent.