Good reply by Chilli Monster regarding London Info versus whatever. Most pilots come to the same conclusion eventually. But it makes me wonder why on earth do instructors make students religiously call London Info with ETA figures etc.
As far as traffic info goes, London Info is practically useless. When I fly in that area, I keep a listening watch on it (in case I have to make a mayday call) but I don't talk to them.
The problem is that one has to keep a lookout anyway, and one can't do it any differently just because somebody has told you there is somebody else in your area. Even with Radar Information, there are many planes (e.g. gliders) which the radar can't see, and many more which have no transponder, or have it switched off, perhaps intentionally. So the argument goes, given that you have to keep a lookout anyway, why increase your workload with a lot of radio calls.