In 1975 Fox was invited, along with Larry Wallis, to start Lemmy's band, Bastards. After taking advice, the band was renamed Motörhead. The band supported Greenslade at gigs, performing cover versions. Their debut was at The Roundhouse, on 20 July. Fox was drummer for six months before being replaced during their first album recording sessions by Phil "Philthy Animal" Taylor. Fox's drumming appeared on the On Parole album track, "Lost Johnny" which, unlike the rest of the songs Fox recorded for the album, was not overdubbed with Taylor's drums.
Lucas also appeared in the band's 10th anniversary video, joining the band on stage for the final number, "Motorhead".
In Spring 1977, Warsaw Pakt formed around Ladbroke Grove, London, composed of lead guitarist Andy Colquhoun of The Rockets, Fox on drums, vocalist Jimmy Coull, John Walker on rhythm guitar, and Chris Underhill on bass. The band gigged around local venues and played with Siouxsie and the Banshees at a gig in the bar of Exeter College, Oxford, Oxford. Their debut album Needle Time was released through Island Records. 5,000 copies were sold in the first week, at the end of the week Island Records decided they would not have any more pressed. The band continued to play locally for a few months more before finally splitting up in March 1978. Following on from this, Fox played for a brief time with the band Walking Wounded.
In the early 1980s, Fox moved to France and ended up booking the music for the Midem festival. This led to him heading an effort by the French Culture Ministry to promote French bands abroad, which was responsible for the international success of bands such as the Gipsy Kings and Carte De Séjour.