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.

Quite wrong as far as new building is concerned. However, there is now the
Access to Neighbouring land Act 1992 that allows access for repairs and
maintenance but it does not allow for new build. Details here
http://www.legislation.hmso.gov.uk/a...20023_en_1.htm