Where can I find population data (male, female, total) for all UK counties for last 7 decades, i.e. 1950,1960,1970,1980,1990,2000,2010. I tried my luck with Office for National Statistics and UK National Statistics, but all in vain.
This is actually more tricky then it sounds! Are you aware that the boundaries have changed quite considerably over the period (not least the 1974 boundary changes - http://en.wikipedia.org/wiki/Local_Government_Act_1972)?
Fortunately the nice people at the University of Portsmouth have done quite a lot of the leg work for you (http://www.visionofbritain.org.uk/index.jsp). So a chat with them is probably the way to go. Depending on your status (are you a student or working in charity / local government?) the data should be available to you free of charge.
Other then that, contacting the CASWEB people at the University of Manchester (http://casweb.mimas.ac.uk/) might be a good starting point. They provide access to Census material going back to 1971 - which I believe is the earliest date that digital micro-level data is available for.
UPDATE With regard to the Vision of Britain resource - a quick play around with their search capabilities shows that the work around they've done is using the country structure until 1971 and then Local Authority structure 1981 onward. This is pragmatic work around to the problem. Some of the boundaries are Creative Commons - but the data would need negotiating (see here: http://www.visionofbritain.org.uk/data/index.jsp).
Population is by Unitary Authority or Local Authority in the UK.
Has Population in Excel Format. You will need to extract that but country (there are tallies for county) then map that to county boundaries.
Use the Boundary-Line (May 2012) shapefile data from here: http://parlvid.mysociety.org:81/os/ create the lines into polygons and then you can map the data by county.