Mr G:
the radar units that will now give you FIS and pass traffic information on traffic that may be of interest will, under BS give you no traffic information unless there is a definite risk of collision
I'm not convinced that's what will happen. Don't forget that traffic info can come in numerous forms:
"G-CD the gliding site at Soarville is active"
"G-CD multiple contacts observed in the Somewhere area"
"G-CD traffic information a Robin DR400 just airborne departing the zone to the west"
"G-CD traffic in your 2 o'clock 3 miles right to left indicating 500 feet above"
Only the last of those is both specific and radar-derived and could therefore - arguably - be the sort of thing controllers won't give you under a BS. But you wouldn't have got it on a FIS either (except very exceptionally). I can't see anything in CAP 774 which stops controllers from giving the other kinds of traffic info.
NS