1) Lennox Lewis - undisputed world heavyweight champ (and born there, ignore the rumours). Would have retired undisputed, but for a technicality.
2) Daley Thompson - consecutive olympic golds in decathlon (went to Moscow beat the Ruskies, went to LA spanked the yanks).
3) Roger Bannister - someone had to break the 4 minute mile, Ross McWhirter was time keeper.
4) Steve Redgrave - no personality but won 5 gold medals (at rowing, athletically impressive if boring).
5) Jimmy Greaves - my hero, more top flight golden boots than any other English striker.
Most overrated in UK: Beckham (obviously), Lewis Hamilton, Flintoff.
I have lived in Canada for many years where Wayne Gretsky is supreme. In Australia it's all Bradman, Warne and Mal Meninga. In Ireland I think Johhny Giles, Barry McGuigan and that Sonia swimmer girl.