Hobbs was born in Preston, Lancashire but grew up in Garstang, a small town 10 miles to the north. In the 1980s, Hobbs lived on a bus in a carpark in Hayes, Hillingdon, with the hard rock band Heretic before becoming a journalist for Sounds magazine at age 19. She later went to work for the NME before going on to help found Loaded magazine. While with the NME she served as UK correspondent in Canada on CBC Radio, filing a weekly music report. This contributed to her big break in radio with BBC GLR, working alongside Mark Lamarr.
Hobbs then worked at XFM before being headhunted by BBC Radio 1 after a confrontational interview on XFM with Radio 1's Trevor Dann. She shot a TV series about global biker culture, Mary Anne's Bikes, in Japan, America, Russia, India, and Europe for BBC Choice & BBC World in 2003, and presented the World Superbikes series 2005 for British Eurosport. She also compèred the Leeds Festival between 1999 and 2003. In the early 2000s she narrated the CBBC science series Why 5.
Hobbs first joined Radio 1 in January 1996, as co-presenter of the weekly Clingfilm movie review show with Mark Kermode. A fan of punk and rock (and with a love of motorbikes) from an early age, she fronted the Radio 1 Rock Show 1999–2005. But her best loved show on BBC Radio 1 was the experimental / electronic show The Breezeblock she created during her fourteen years at the network. In September 2006 The Breezeblock name was dropped for the title Experimental. Hobbs was an early champion of the dubstep and grime genres and hosted the legendary 'Dubstep Warz' special on BBC Radio 1 in January 2006.
Hobbs returned to radio in the primetime slot (7 – 10 pm Saturdays) she always coveted for electronic music on 9 July 2011, broadcasting from XFM in Manchester. In September 2011 she began hosting the relaunched "Music:Response" evening show across the XFM network. On Wednesday 31 October 2012, she announced live on-air and on her Facebook page that she was leaving XFM the following day.