any
legal issues I need ot be aware of in case the neighbours get
unfriendly?


At Common Law, anything hanging into their space (across the boundary) is fair
game and they can lop it off even if it should later kill your tree/bush.

For those wanting to do the pruning, first for heaven's sake talk to your
neighbour and tell them what you want to do - most neighbour disputes arise
from lack of communication.

If they don't agree, give written notice to the neighbour and ask them if they
want to be there while you do it. And have a witness there!

As a lawyer that dealt with a half dozen of these cases within a couple of year
period (it seems to have calmed down now), let me add a bit of advice -
neighbour disputes are, next to divorce and estate proceedings, the most
bitterly fought battles even when it makes the least fiscal sense to be
fighting.

Have a witness and preferably take pictures or better yet video of you
trimming. I had one guy that whacked the neighbours tree quite legally, but
failed to take this little precaution, and wound up spending money going to
court over it. Just think about what happens when you cut a fairly decent
sized bough right at the property line. Yup - it springs back, and then your
outraged neighbour can take pictures to court showing the result - the cut
branch that sprung back a couple of feet into his yard - and allege that you
trespassed and cut too much. You may (and should) win, but it is going to cost
you!