[heero_yuy]

You should be able to do this yourself: The consumer unit should have a large earth terminal block on the panel. In town the braid of the incoming electric supply is bonded here. In rural areas this runs to an earth rod just outside.

An earthing clip and some 6mm yellow/green cable from the metal gas pipe to that block will do the job.

There should also be a similar cross bond to the incoming water main.

This didn't used to be needed but with both gas and water mains being replaced with plastic the metal piping, sink, bath, shower etc. all need to be cross bonded inside the house. This is an important safety issue.