This is a fairly fundamental part of flying. The class of airspace may affect the details of the answer but, essentially, ATC provides separation between IFR aircraft. There is no separation to be applied between VFR flights or between IFR and VFR. ATC should, subject to workload etc., give the IFR flight traffic information on the VFR flight.
Having said that, many controllers will build some space between VFR and IFR flights by means of the clearances issued to the relevant flights. This is partly because it makes things safer and because it reduces the need to pass traffic information.
It must be said that the airspace allocation used in the UK makes the mixing of IFR and VFR flights more common than in other States.
You asked the question about separation - and you have an answer. Whether the situation you describe is good controlling technique - or the optimum way to handle the traffic situation - may be questionable but that's another issue.