The original question was "who was the most famous English athlete of all time". Trick question; Famous & Best are two very different categories, although not mutually exclusive.
Could it be that Famous = Media Coverage. In which case it must be an athlete from the past 1 1/2 decades with 24/7 media coverage in the most remote areas of earth.
I propose it is impossible to reach an answer due to the problems involved in knowing which English athlete does or does not get coverage in China, Ethiopia, Bali, etc..
HOWEVER.. Gordon Banks would get my vote as the Best English athlete. ;P