Why on earth would a VFR flight request a PS? They won't get it from a radar unit unless the radar's u/s and if it's from a non-radar unit they would have to be sure they could either accept flight in IMC or be sure they wouldn't encounter IMC. In any case if they're already in contact with a unit that's providing a PS to someone else, they'll hear that PS traffic getting traffic info on them, so what would be the point in getting a PS themselves? But in no circumstances can a controller giving a PS give traffic info on aircraft not speaking to him so BS traffic which is already on frequency can gain nothing by asking for a PS.
Thinking of some of the non-radar IFR airfields around the UK, I simply don't believe that the advent of BS from 12 March will lead to controllers no longer giving traffic info on IFR arrivals/departures to the potentially conflicting VFR traffic they have on frequency. It just would not make any sense and I can't see controllers agreeing to do such a thing.
NS