Poullain was the only original Darkness member not from the Lowestoft area. Before joining the Darkness, he worked as a tour guide in the Venezuelan mountains.
Poullain left the band on 23 May 2005, citing "musical differences" as the reason. He was replaced by Richie Edwards, a former guitar technician for the band. His departure caused quite a stir with the press, most notably in the NME magazine where he was reportedly regarded as their favourite member of the band.
However, in 2011 The Darkness officially announced that they were to reunite, with all 4 original members. Frankie described this as being "Just like old times". The band sub-headlined Download Festival at Donington Park, England in June 2011, playing under Def Leppard. They also played at Hammersmith, with Queen guitarist Brian May joining the band. The band's third studio album Hot Cakes was released in early 2012, as the band embarked on the Hot Cakes tour.
Frankie's autobiography Dancing in the Darkness (John Blake Publishing), charting the ups and downs of life with the band, was released in November 2008.
He plays a Gibson Thunderbird IV bass guitar (nicknamed "the brown bastard"), recognisable for its reverse body design. When playing live he allows natural distortion to take place for effect. He also uses a Fender Precision Bass, Ampeg VT, Mesa Boogie, 50 watt handwired Marshall guitar combo and a Sans Amp bass driver.