Each Health and Social Care Trust will have its own policy, so the rules might differ.
In Belfast, for example, each patient can have two nominated people who can visit them throughout their stay in hospital but only one of those two people may visit on any particular day (and then only once), with an appointment needing to be made in advance:
https://belfasttrust.hscni.net/2021/10/07/update-to-visiting-guidance-oct21/
It might be different elsewhere in NI though.
It’s probably different to here but I’ve recently been in hospital in Greater London for around a month, and I was only allowed one visitor at a time, though it could be a different visitor each day, still only one at a time.
Depends on which hospital, which ward etc.
Best person to ask is the person you want to visit.
A friend of mine was in hospital and the ward she was in at first said no visitors, then she moved to a different ward and was told 1 visitor, must be a relative, and only that same person every time.