In the interests of accuracy, Royal Mail have
never previously issued stamps to honour championships: neither Mansell nor Hill had a special issue devoted to them (although the Isle of Man produced a set for Mansell, who lived there at the time). As this article from The Times points out, for many years it was Royal Mail's policy not to depict living non-Royal personages on their stamps:
http://business.timesonline.co.uk/tol/b ... 176517.ece
The first non-Royal on a British stamp was William Shakespeare in 1964, followed by Sir Winston Churchill in 1965.
Last year, Royal Mail did issue a set commemorating both the centenary of Brooklands and the 50th anniversary of Stirling Moss' win in the British GP, but IIRC this is only the second motor sport themed set they've ever produced.