Former Free rockers Andy Fraser and SIMON KIRKE are hoping British Prime Minister Tony Blair will accept their invitation to perform with them at a fundraising gig. Free are Blair's favourite band of all time - he once said if he could sing like vocalist PAUL RODGERS he would never have entered politics. And Fraser and Kirke want the British leader to play guitar with them at a forthcoming Free tribute gig benefitting the Nordoff-Robbins Music Therapy Foundation, held in memory of the group's late guitarist PAUL KOSSOFF, who died in 1976. It is not currently known if Rodgers will attend the event.