Range from the cheapest Fit a new plug socket £110 (Sam electrical based in Nw1) to the dearest Fit a new plug socket £230 (Novalux Electrical Services Ltd based in SW1Y).
Comparing electricians estimates for a Fit a new plug socket gives you an idea of who will be better value but the best way to compare costs is to get actual quotes.
What to do - Get rates and quotes by posting your job to fit a plug socket to electricians in St James's.