Earthing a new consumer unit

All incoming services whether they are Gas, Water or Oil require equipotential bonding which need to be routed back to an M.E.T (Main earthing terminal) which can be within or external to the consumer unit. This is a requirement of the wiring regulations and ensures that anything providing a route to earth is of the same potential. The only time this is not required is if the incoming service uses a plastic incoming pipe as this obviously does not provide a path to earth. I hope this brief explanation helps. Best regards Kev @ KRT Electrical Services

Check whether you have a plastic blue MDPE water pipe coming in to the house. If you do you don't need any bonding to the water pipe.

Sounds like you have been given good advice, anyone quoting without checking this isn’t doing it right. Metallic gas or water services must have equipotential earth bonding installed within 600mm of where the pipe enters the property or within 600mm of the gas meter (customer side) and within 600mm of the main water stopcock. If the stopcock is some way into the property it is preferable to site the bond where the pipe enters the property. This as far as is reasonably practicable should be done before any branches in the pipework and in a location where it is easily accessible for testing and maintenance purposes. A plastic water service need not be bonded but only if it can be proven by way of testing that internal metallic pipework does not introduce an earth potential, the regs suggest it may be preferable to bond internal metallic pipework supplied from a plastic service where this cannot be proven.

In contrary to most comments if the installation is in 4mm which I assume it is given the case. Then the installation stays to the regulation on which it was put in yes regulations state 10mm bonding and 600mm or before first T or elbow but during the original install if it requires 4mm and they installed nearest practice at the time then it's fine unless you change the characteristics of the properties means of power (change the mains board) if there is decent continuity on the bonding what is in and you haven't changed the mains board you aren't bound by law to have it installed.

The water pipes and gas pipes need to be bounded where they come into the house

If you were to upgrade the consumer unit then the earthing of any incoming metallic services (Gas, water, oil, metal structure) would have to be upgraded to 10mm if not already in 10mm. The reason for this is to keep all extraneous metal parts at the same potential. The electrician who quoted for you is correct.