Thanks for all the ideas, I have decided to stick with covering any problem area with metal mesh, and try the citronella spray short term. I won't get a sonic device as I do not want to risk affecting nearby people or wildlife.
I've just seen a neighbour's cat chasing a grey squirrel along the top of our fence. The cat does poo in our garden from time to time but she's forgiven as long as she keeps the vermin down.
Doncaster, South Yorkshire. Soil type: sandy, well-drained
Posts
I live in west central Scotland - not where that photo is...