I have a number of doors in the building that I manage which have fairly old steel hinges that work fine but have been painted (probably on many occasions). As this is an old building and im not fitting new door sets, are the doors still within regulations if ok in all other respects ie gaps, seals, closers and latching?

If your Fire Risk Assessment states that original notional fire doors are OK (which in can in several circumstances in line with official guidance) then as long as they are maintained in working order they should be OK