The massive misunderstanding is all this "traffic info" stuff is that the known traffic they tell you about is only the tiny fraction of the actual traffic which happens to be talking to that unit.
There is traffic potentially anywhere, and the UK is fairly busy GA-wise. This is why I find it bizzare issuing notams on military traffic in such and such area - they can be anywhere anyway! And they can and do look after themselves. There is no meaningful avoidance which a GA plane can do against a 500kt jet - especially as a target on a genuine collision course will be a stationary point in the sky and will not be seen until too late. The jet has his own radar.
Only a radar ATC unit is able to provide a meaningful service. All that London Info can give you is "13 aircraft known in your area" with no real time aspect to it. And those will be mostly PPL students, mostly flying at ~ 2000ft or below. The other 200 they don't know about.
And if everybody called up London Info, the service would immediately collapse. They can sometimes barely cope as it is, on nice days.
UK mid-airs over the last 10 years average 1 per year, and all but the last one were below 1000ft AGL. The last one was alleged to have happened at 1800ft. These are very low levels which nobody should be flying at (outside the circuit) unless taking photos etc, and suprisingly don't at all correlate to well known airspace bottlenecks such as the 2400ft under the LTMA.
Last UK IMC mid-air was in WW2. No doubt, this is due to the far lower traffic density in IMC.
Technically it would be trivial to deliver a radar feed to any airfield, over the internet. But the job demarcation in ATC (higher salaries for radar qualified operators, etc) means this cannot happen in the UK. It is done abroad. It is already easy to get this info with a sub-£1000 ADS-B receiver box but a) this picks up only targets emitting their position on the 1090ES channel (which are all Enhanced Mode S installations i.e. 250kt+ turboprops and jets and above) and b) the airfield would not be allowed to provide a service based on the info. Let's hope that Eurocontrol don't get the idea of mandating Enhanced Mode S for GA as this will be impossible! But they are gunning for mandatory ADS-B which is bad enough.