Meanwhile, my ongoing battle with Jerry continues. I was always suspicious that the bait hadn't been taken and in fact all it did was make him tiptoe more lightly around the kitchen. Confirmation came after I scattered a little flour on the floor, expecting to find ickle paw-prints in it the next morning. Sod that - he came and ate the whole bloody lot! So the snap traps came out, and again he's proved himself to be a canny bugger and has steadfastly avoided them (despite one of them fitting snugly inside his entry channel).
It turns out that the right thing to do is to call the landlord's agents, who have a dedicated mouse man who'll come out, do a thorough investigation and block up all the hole. So this should all be over soon I hope...