This GPO film makes facinating viewing- it says it was made in 1969 but the fact it was made by Post Office Telecommunications and the reference to the New Penny makes it more likely to be 1971ish.....
Seamus
http://www.youtube.com/watch?v=qqtoVmACDng
As far as im aware this never went beyond the planning stage......
And to think, the internet supplanted their ideas for such a system of remote banking, video calls, working from home and whatnot... :D