Of how much practical benefit will that be? It isn't realistic to navigate around the London area without having to break off from LARS to get ATZ transit information/clearances and local movements.
Yes we could all go steaming around relying on DR and see and avoid. However there is evidence that for many this does not work. If you want to do so and believe it is safe to do so - then that is up to you. In the first case if your skills are adequate, it clearly is safe, in the second I am afraid the evidence is very much against you.
There are many (including me) that believe the use of moving map GPS (with adequate training) would avoid a lot of CAS busts.
There are many (presumably including NATS) that believe a London RIS would also avoid many CAS busts and reduce the risk of collision. (I also agree).
Why on earth anyone would want to dismiss a genuine initiative to improve safety so that is not going to cost them a single penny defeats me.
Moreover, if you think you are going to steam through someones overhead, and by talking to them on the radio believe this is going to help their local traffic and you avoid each other then you are dreaming. Please read what IO540 has to say.
IO540 also has a sound point about POV - the trouble is it as you gain experience you can forget that when we all first learnt your nav skills can let you down. RIS provides AT the opportunity to avoid CAS busts before they have happened. How often (for whatever reason) do we hear those people who are sensible enough to ask for a RIS - G-XXXX if you continue on that track / height you will infringe CAS. Secondly, and unfortunately, there remains a strong anti transponder lobby. Whatever the merits of their position on this, all the time a significant part of the traffic is not transponding TCAS is not a complete answer. I also accept that cost will remain a significant consideration for some (and understandbly so) for a time to come yet.
In conclusion, IMHO a very well done to NATS for attempting to provide and integrated RIS around London. I for one are very grateful and believe if pilots use it (and in particular it is many of the low timers who need it most) it will be a significant step forward in reducing the risk of CAS busts and will avoid an wholly unnecessary mid air.