On Fri, 04 Mar 2005 21:57:39 GMT, (Peter)
wrote:

snip

There is a very good reason the neighbour should not build such a
'trespassing' extension. It can come back and bite when he comes to
sell the property. The purchaser or his mortgage company could well
throw a spanner into the works at a most awkward time if this is
discovered as it is likely to be.

Even if you decide to agree to it, it must be properly set up on a
legal basis and you need your own solicitor to assist - it is quite
reasonable for the other party to meet his fees. Do not rely on his
solicitor to handle both ends - there is a conflict of interest with
this.

This gives you a valid reason to discuss it with the neighbour in such
a way as to do least damage to relationships.