I mean VFR - the issue is whether a particular aircraft needs to maintain Instrument Flight Rules or not. If it does, whether it's visual or not, it needs minimum separation
Not from VFR traffic, Genghis. In class D, which is the only low level controlled airspace a VFR flight is likely to be doing circuits in in the UK, IFR traffic does not
have to be separated from VFR.
However (from MATS Pt 1):
Instructions issued to VFR flights in Class D airspace are mandatory. These may comprise routeing instructions, visual holding instructions and level restrictions in order to establish a safe, orderly and expeditious flow of traffic and to provide for the effective management of overall ATC workload.
Aerodrome control is responsible for issuing information and instructions to aircraft under its control to achieve a safe, orderly and expeditious flow of air traffic and to assist pilots in preventing collisions between: [virtually everything 
]
This implies, I think, that if ATC thinks that it's safer, more orderly and more expeditious to let the 747 preceed the C152 to avoid the 747 going around, it has the right and the duty to issue instructions accordingly.