-
The boiler is close to the entry for the gas pipes (in fact I think the only gas pipes are in the kitchen where the boiler is). This is what I got from the electrician.
Install main earth bonding conductor.
It is not uncommon this conductor missing, as it was not required in older versions of the wiring regulations, or was not fitted during conversion work or re plumbing not supervised by an electrician. It's purpose is to connect together the incoming main earth with all the other conducting services entering the flat, in this case the gas, water and electricity. This will prevent any dangerous differences in voltage between pipework and electrical systems in the event of a fault. These connections are essential before any other new electrical installation can be done. Supplementary earth bonding will be fitted to the hot water and heating systems at or near the boiler if not already fitted. The new earth wire will run from the consumer unit to the boiler where it can pick up all services in one place.
The new cable will be surface wired most likely as discussed by running a cable along the staircase and hallway skirting board and then into the kitchen.
aggi-
Yes, main bonding is often missing and has just become a reg. If you had said you needed main bonding to the meter/entry point for the gas it would have been less confusing. 10mm earth bonding surface mounted! Wouldn't get that past Mrs Airhead.
You do need it done though if you want a new CU. Going back to your original question, you can do it yourself, your electrician only needs to check the continuity. It should be one piece of cable, no joining allowed, so make sure you buy enough to reach.
Airhead
Earthing for the boiler would be supplementary earthing so could be linked to the rest of the supplementary earthing in the property, it doesn't need to come all the way back to the MET (cu earthing connector).
Main bonding is required close to the entry of the water pipe and the entry of the gas pipe to the property. Do you need this long run because you have no other supplementary bonding or because the boiler is close to the entry of the gas/water pipe?
Some older installations have very little supplementary bonding and now it's stopped being a requirement in bathrooms so I can see how you might need a long run but normally the boiler is earthed by the gas and water pipes and bonded by the 100cwt of steel they are connected to.
Try searching for "requirement for supplementary bonding on boiler". The recent IET forum threads are very useful. I can't remember boilers being mentioned in the regs so it's possible you need to check the source of your information about it being required, hopefully it's not your plumber!