Some notable successes since WW2
Sir Alf Ramsey (England - World Cup winners; Ipswich League champs)
Arthur Rowe (Spurs - League champs)
Bill Nicholson (Spurs - League champs +8 more major trophies)
Vic Buckingham (WBA - FA Cup winners, League runners-up; Ajax - League Champs, Barcelona - League Cup winners)
Dave Mackay (Derby - League champs)
Graeme Souness (does he count?) (Rangers - 7 trophies. Liverpool - 1, others - 3)
Terry Venables (Spurs - FA Cup winners, Barcelona - La Liga champs + Spanish League Cup)
Several ex-players have managed national teams
Ramsey (England)
Mike England (Wales)
Venables (England)
Glenn Hoddle (England)
Klinsmann (West Germany, USA)