Wiring regulation 132.16 says something along the lines of:-
"NO alterations, temporary OR permanent should be carried out without first verifying the condition of existing equipment, protective devices and earthing and bonding are adequate for the proposed alteration."
It sounds to me as though your electrician is carrying out appropriate due diligence before amending your electrical installation..
Many, builders, DIY'ers, Kitchen fitters, cowboys etc.. often omit these essential checks.
Any idiot can join a few wires to make something work...
But as electricity can KILL a healthy adult in less than a second all alterations should be designed to fail-safe and NOT endanger any persons using the installation.
Checking earthing and bonding are essential safety checks NOT optional.
If new earthing and bonding are needed, the actual method(s) used can depend upon the Material cost, Labour costs, Building structure, Competence of the person doing the work etc.. etc.. It is a bit difficult to advise over the internet without seeing an actual property..
BUT for many many years, basic guidance for any proposed work in your home, (Gas/Electric/Building/Decorating etc.)..
IS get at LEAST three independent quotations before making any decisions to accept any contractor.
Hope that helps..
And Welcome to the interweb forumbulator..