Covering the years 1858-1959. These are already available on ancestry, and free on the government site, but Findmypast have indexed the full text (I assume using OCR software), so you can search for the names of executors or administrators (using the "Full Text Search" box), not just the name of the testator. I have been waiting so long for someone to do this! You can also search for addresses.
http://search.findmypast.co.uk/searc...925.1289493982
Please note that the testator's name (i.e the person who died and left a will) will be indexed in the form Surname First Name Middle Name, e.g. Smith John Albert for John Albert Smith. Or if there is no middle name, just Surname First Name. So you will need to search for the name in that format or it won't pick it up. But the executor or administrator's name is indexed in the normal format.
They also have a browse facility, though of course you could just browse on the government website:
http://search.findmypast.co.uk/searc...925.1289493982
Government website, please note the date tabs:
https://probatesearch.service.gov.uk/#wills