Build over sewer - have I covered all bases?

dbuk44

Hi - hoping for some help from people who have been through a build over sewer.

In the third week of Jan our builders will be constructing a single story extension over a sewer at the back of the property.

So far I have got;

1. Planning permission (needed this anyway, but was also fed this into the application with the water company)
2. Buildings insurance permission in writing
3. Legal agreement from the water company - and a letter subsequent to the agreement paperwork saying I can proceed
4. Agreement from the mortgage company, both as a party to the legal agreement with the water company and separately in a letter to me directly
5. Plans and method statements from the builder, stamped and approved by the water company
6. A pre-build inspection of the pipe with a camera prior to the builders starting work. The water company are also coming to do an inspection once the ground is opened.

Have I missed anything?

Has anyone taken out any form of indemnity/insurance should any time after the build completes the water company want to dig up my extension floor (as the agreement allows them to)? Was this via a solicitor?

NB: the outmost wall of the extension is just on line with the pipe, and there is also good access from 5m either side via manhole - so whilst not likely they will need to dig up the floor, it is still a risk.

Thanks all !