Hi,
There is a cat fitting this description, (mainly white with tortoiseshell patches & "squirrel like tail with markings") who lives on Knapdale, the two blocks of flats adjacent to Taymount ... not sure if male or female but is out a lot. I have seen it around (from Shackleton Close, which also backs on to you) and sorry to hear it's a pain

Spraying is stinky and apart from that (if it is the male causing you probs. & the one I see out) it will probably be impregnanting female cats that other owners have not bothered to have spayed. That's what happens when you get a cat and let it out to roam but do not bother to spay or neuter it. Bad pet ownership/care

Good luck!

Regards
Sue
A sympathetic human "owned" by a non-roaming/neutered cat