Right of first refusal - buying divided house with Freehold - pitfalls

[Rollerbird]

Looking at an upstairs flat in a semi - detached house, buying to let. The downstairs flat is lease (owner occupier)and the vendor of the upstairs flat is the freeholder.
How does the rfr work?
It's not been mentioned but i noticed it while googling. Should we bring this up with agent and owner of downstairs?
How would you know the value of the Freehold?
If we bought the flat without them being offered it, then they said they did want it- how would it be valued?
The freeholder has never asked for ground rent and we are happy for this to continue but obviously need to know our responsibilities under the terms of the lease.
Advice?

Any ideas?

Do you mean that the upstairs flat owner also owns the freehold of the entire property? So I suspect the upstairs flat freehold owner has granted a long lease to themselves - the owner of the upstairs flat.
That is similar to one we know. In that case it is 3 flats - 3 floors with 2 of the long lease holders/flat owners also owning the freehold but one flat doesn't.

In that case when repairs are needed the freeholder and leaseholder share the costs. They all share insurance premiums. No need to ask for a ground rent.

Would you be buying the freehold along with the upstairs flat?

Yes it is being sold by someone who is living abroad and rents it out.
We would want also to rent it out.
I didnt realise the freeholder would 'lease' the flat to themselves?

Too late for this.
Apparenrly the owner sold it to a friend in the Uk.
(but Im ok with it incase of issues ref my question - there will always be another one!)