JimGannon made a double switch at half-time with Keith Lasley and Jim O'Brien coming on for John Sutton and Forbes, and Jamie Murphy moving to play through the centre.
Manager JimGannon had played in all four previous defeats but can savour a deserved victory for his team in what was the most exciting play-off final of the weekend.
Posh appointed JimGannon after Cooper's dismissal last month but Holdsworth's stock will rise dramatically after inspiring County to become the first side this season to be promoted in the English pyramid this season.
McGhee's former club, Motherwell, cashed in by selling David Clarkson and Paul Quinn in the summer and new manager JimGannon thought he could cover that by raiding some of his former rivals in that same division.
New Well boss JimGannon has already won over the fans thanks to his attacking style of football, his candid post-match interviews and the fact he's willing to drop established players if he feels they aren't pulling their weight.