Business names
You have a list of businesses by name and nothing more. Names alone make for a fuzzy match — expect to do some cleaning — but they are enough to reach the company register and work up from there.
Business Rates (Non-Domestic Rating List)
The names of businesses you deal with — The occupier name is often embedded in the composite address string — a fuzzy match, not a clean join
Charity Register (England & Wales)
Charity or organisation names — Match on registered name; expect some cleaning as names vary
UK Company Register (Companies House Company Data)
A list of business names, with no company numbers — CompanyName is stored uppercase with no original casing; matching by name alone is fuzzy and needs normalisation
Public Contracts (Contracts Finder)
Supplier or buyer names — Match on the named supplier or public-body buyer; expect some cleaning