Some interesting economic graphs of the Thatcher years here, Matheous, including unemployment figures. I seem to remember the highest number was during 83-85, where it was around 3.2 million at its highest.
Not sure that you can necessarily do a direct comparison with todays figures though, because of all the categories where you are not officially classed as unemployed,although in receipt of welfare, but in some form of training, or work experience or whatever..
http://www.bbc.co.uk/news/uk-politics-22070491