IMHO the cheapo unit which does not tell the direction is worthless. The one to look at is the next one up which tells you the quadrant.
If transponders were mandatory I would buy a TCAS system right away. But they are not, and one has to view the situation in that light. So far, nearly all UK mid-airs were below 1000ft (only the very last was higher; 1800ft reportedly) and all since 1942 were in VMC.
So, now you know where to fly to be safe
Above 1000ft, and in IMC if possible.