leasehold: self contained residential flat in one occupation

I am looking at a leasehold for a property that I want to let to multiple tenants as an HMO. It would qualify for planning purposes, but I have a worry about the leasehold document (written in 1987).

One clause says
"to occupy the flat solely and exclusively as a self contained residential flat in one occupation only."


Does anyone have experience of this language? It could mean that I can't sub-divide it into more than one self-contained flat, but it could also mean that it can't be let to more than one household.

Should I ask for a variation on the lease before I purchase the property?

thanks,