That was the point I was trying to make earlier, you seem to have proved it by not inheriting your Dad’s Cockney accent, but instead were ‘infected’, probably for life, by your Leicester school friends. Of course the fact that he ‘never quite lost’ his Cockney accent also strengthens the case, he obviously retained elements of his two local accents.
School is the key and who you mix with there. My primary school was for 1 year in Southampton, 1 year at junior in Manchester, then all the rest in Notts, which is where I got this EM accent that I can’t notice till I hear a played back recording. 
As to the football, I lost interest many years ago, disillusioned by the big money coming into the game. Most of the ‘clubs’ should not be called clubs anymore, imo the word club refers to an association owned by its members, in this case the regular fans (the German principle I think), whereas many in the Leagues are owned by big business or rich foreigners, or both, and run as money making businesses. But I do take a passing interest in international games but don’t watch more than a few minutes before becoming either bored or over-stimulated on tenterhooks. 