Catch it in one of those non-fatal traps then call over to the house/flat of some horrible person you know, but for some stupid social contractual reason, you must must socialise with. And when they go to make you a coffee, or go to use the loo, unleash the mouse! Presto! No need to make a trip to the countryside, no need for a cat, no worries about the mouse realising that you can't bring yourself to kill it and the mouse probably won't care who's left over wasabi peas it's eating. And you get to stick it to some asshole who probably deserves it. Win-win