Any advice on how to keep them out of the garden would be greatly
appreciated, i'm tempted to catch/trap them & put collars with bells on
them, that way i'd know when they're around.

I used to love seeing squirrels until I had a two-month running fight,
trying to get several humanely out of the loft of a bungalow I moved into,
and which they were "wrecking".

After two months my tactics had to change, and there were a few less around.

If I see one now, they'd better keep long distance from me....

Greatest laugh recently was in a London restaurant seeing on the menu,
"Stuffed Squirrel". I didn't sample it, but hope it becomes popular.

They're just cute looking, evil rats!!