Starlover - I don't think it will count if they have just stripped back the existing boards as building regs usually cover only alterations to existing buildings and new buildings, i.e. they do not apply retrospectively.
You are more likely to find the answer you need in your lease agreement. I assume that you either share the freehold, in which case there should be an agreement or have a lease from your freeholder.
Depending on when the lease agreement was written there may well be a clause in there about not having bare floor boards on upper floor flats without installing appropriate installation. In fact many leases stipulate that the floors and stairs must be carpeted.
I'd have a look at the lease and then go to the council if that doesn't reveal anything!