I think that the point being made was that Heath must have been aware beforehand somehow that Hayden owned a property in Cambridgeshire. He then searched the Land Registry for that address.
The question is though, how did Heath become aware of that address?
The allegation appears to be that Heath had gained access to Hayden's information held by Experian through creating a fake account with Experian purporting to be Hayden.
It was said that the Experian information contained the Cambridgeshire address as some sort of linked address to Hayden.
It was said that this is the only way that Heath could have learned of the Cambridgeshire address and so it must have been him who created the fake Experian account.
The only other way to search the Land Registry without knowing which particular property you are looking for (or even which part of the country it might be in) is by doing a search of the Index of Proprietors Names.
If you search for an individual (rather than a company) then you must have a specific reason for doing so. For example, if you are an executor and you are checking what properties the deceased might have owned or are tracing the assets of a bankrupt person.
Other than that, an individual requires a court order to search the Index.
I believe this is what Hayden was talking about.