Granger graduated in History of Art from
University of Manchester. She then became a vintage design dealer, specialising in furniture and lighting from the 1960s and early 1970s. During this period, she started buying lava lamps from the original factory in
Poole and selling them at
Camden Market. She was offered the opportunity to take over the original
lava lamp business by inventor and owner
Edward Craven Walker and his wife Christine. Alongside business partner David Mulley, Granger spent the next ten years repositioning and growing the
Mathmos company. They bought out the Craven Walkers over several years, with Edward Craven Walker remaining a consultant until his death in 2000; Christine remains close to Mathmos.
Mathmos grew strongly during the 1990s, with British-made
lava lamps finding a worldwide audience. Mathmos won a host of Business and Marketing Awards, including two
Queens Awards for Export. In 1998, David Mulley left
Mathmos, and Granger became Mathmos's sole owner and
Managing Director. The following year, she was on the shortlist of four for the
Verve Cliquot Business Woman of the Year Award. Granger spent the next decade diversifying the business into different ambient lighting products with a team of internal and external designers. This won Mathmos new customers and several prestigious design awards. Mathmos retained its British manufacture of the original lava lamp range, gently expanding it to include new models. Around 2010, Granger decided to narrow Mathmos' focus to its quality lava lamp range and to focus on
direct to consumer sales. Mathmos now directly supplies customers all over Europe with its much-enlarged range, from small candle-powered lava lamps to giant floor-standing versions. In 2023, Mathmos celebrated its 60th anniversary by opening a factory shop in its original home in
Poole, Dorset. Granger and the Mathmos team also worked with five creatives, including
Duran Duran,
Rankin and
Sabine Marcelis, to produce limited edition customised versions of its classic 1963 design Astro. ==Creative industry activities==