In article ,
"Peter Crosland" writes:
The first thing is to discuss your concerns with your neighbour. If he is
not responsive to your objections then write a letter to the council setting
out your concerns about the planning aspects. remember that even if he does
get planning permission then that does not mean that he has carte blanche to
build since he has to obey the law regarding trespass and the Party Wall
Act. He cannot force you to give permission to allow access for building in
any way.

I don't believe this is right. I can't tell you which law
covers it, but there was a case in a local paper ~15 years
ago where exactly this happened. I believe you are required
to provide reasonable access to neighbours for building and
maintenance at the edge of their boundary. It required only
a quick trip to court to get an order to enforce it, whereupon
the builder was granted 6 months unrestricted access to the
neighbour's garden for the building work, and the neighbour
lost all right to negotiate such access for that period.
The order also required unrestricted access for transportation
of building materials, which due to the layout of the
neighbour's plot, meant they strictly couldn't even park
their car on their driveway during that period.

The Party Wall Act is available here
http://www.hmso.gov.uk/acts/acts1996/1996040.htm and note the sections
regarding adjacent excavation and construction.

That is more recent than the case I'm remembering, and some
aspects of it may have superceeded earlier legislation.

--
Andrew Gabriel