I know some people are going to suggest that this is cruel, but couldn't you use something like a smoke grenade or smoke cannister? Serious suggestion here - non-lethal at the end of the day.
Not sure what the law is in regards to these - I know it's illegal to move nesting birds and bats, but not too sure about the tree rats you;re having problems with.
What colour squirrels are they? If they are greys they are classed as vermin and can be treated as such. If they are reds they are protected species and must be treated as such.If they are reds (unlikely as they are quite rare these days in most areas) I'd inform the council and find out just what you can and cannot do in regards to shifting them