OP here, for the original post about rats. Thanks so much for all the
good advice an experiences shared.

I bought poison (Rentokil, from Tesco) and set it in a drainpipe where
hopefully only rats will find it. It is being eaten.

I also bought a pair of traps (also Rentokil: cheap plasticky things
(did I say cheap? nearly 8 quid, but the only ones available)).

The traps have killed 3 rats in 2 days. Yikes. Urgh. Etc. [1]

Unfortunately I suspect the ones in the traps had a go at the poison on
the way the what a waste!

John

[1] I took the bodies in a carrier bag to the local tip (waste sorting
station) so that nothing else would eat them (being poisoned as well as
pole-axed). I figured a couple more dead rats in the landfill won't
really be noticed.