[1] He then competed in twelve rounds of the Formula Renault 2.0 UK in 2005 for Team JLR, without great success; finishing 26th overall.
[2] Firth returned to the cockpit in April 2009, partnering Nigel Moore in the British GT Championship, driving for Team WFR in a GT4-class Ginetta G50.
[1] Firth also entered all five rounds of the Le Mans Series in 2011, driving for TDS Racing and partnering Mathias Beche and Pierre Thiriet in a LMP2 class Oreca 03.
[12] The team took two class wins, at the 1000 km of Spa and 6 Hours of Estoril,[13][14] and finished fourth overall in the LMP2 championship.
[16] For 2012, Firth and Hughes joined Murphy Prototypes, who entered an Oreca 03 in the European Le Mans Series (ELMS),[17] with Luca Moro also sharing the drive.
[18] Firth also drove for Team WFR in the British GT Championship, partnering Riki Christodoulou and driving a Ginetta G55.
[24] His ELMS season was a little more successful, with a third place during the 6 Hours of Donington being the team's best result in the series (Brendon Hartley having replaced Moro).
[31] On 16 April 2013, United Autosports announced that Firth would be replacing the injured Richard Meins for the rest of the British GT season, partnering Mark Blundell in a McLaren MP4-12C GT3.