Thank you Gonzo-you are one of the stars of Pprune and I certainly learned a couple of things about what goes on over my head from your post.
For others here , all I was trying to say on this point, is that the current situation, i realiise it is not actually always intentional, is fine as far as the public are concerned in the area south west of LHR - if things can be elft like e that there will be no real complaints and that has to be a bonus for everyone. So infact people will not vote for concentration, on SIDs at least, as long as it is elsewhere but -as most people in this area realise LHR is a very valuable part of the economic community of N W Surrey E Berks and N hants. They will happily accept a degree of background minor nuisance noise as they have done for years-so if it is possible to retain some form of dispersion it will stop complaints occurring and everybody will be happy. Its not NIMBYism, or a sort aviation luddite view of variable and wavering signal VORs and NDBs and old fashioned analogue instruments just a plea for a bit of common sense and thought for people on the ground who largely support LHR when designing things for the future