" wrote:

We were planning to dig down 750mm (exposed to strong winds) and
concrete wooden posts in. What's the best way of digging the new post
holes and not damaging the sewer pipes?


Divining could tell you where the sewers are, and help you avoid them.
Your local water company responsible for drainage in your area should
be able to help. They might even locate them for you, probably free
of charge, in order to avoid any disruption to their pipes.

Alternatively, try a divining course yourself. There are courses all
over the UK:

http://tinyurl.com/66uf8j

I am very sceptical by nature and thought divining was a load of bull
until someone taught me how to do it. After about half an hour I
could locate all kinds of underground services. I could not believe
how easy it was, and so far, it also seems to be quite reliable.