Bit of an update;
Some news items mid September 2012 suggested Cameron and his new Transport Secretary had killed off the idea of an 80MPH limit for certain GB motorways; news example of this-
http://www.dailystar.co.uk/posts/view/272593
But, always best to check Government directly for actual progress; this October 22, 2012 Pdf from "The House of Commons Transport Committee",- discusses the issue further, and you can see how the roads agency proposes to proceed:-
http://www.publications.parliament.u...an/648/648.pdf
NON pdf of same:-
http://www.publications.parliament.u.../648/64804.htm
And so it goes.