".............If I am right don't try to pull them up if the infestation is
widespread -they sucker like mad. I would spray the after they leaf out, but
of course this will kill the whole plane and the neighbour may not like
that. .............."

Chop through them along the boundary with a spade then spray your growth,
this way it cant get back to your neighbours plant.

--
David Hill
Abacus nurseries
www.abacus-nurseries.co.uk