Dimmock is a former pupil of Wellow Primary School and the Mountbatten School in Romsey, Hampshire. Her father was a merchant seaman, and her mother Sue, ran her own clothes shop. When she was at school Charlie wanted to be a forensic scientist.
Dimmock first came to the public's attention in 1997, when she joined the BBC gardening series Ground Force. Dimmock met the producer/director of the series five years previously when she built a pond for the Meridian series, Grass Roots. Dimmock, who is well-endowed, became known for going braless in all weathers.
Since then, she has presented such programmes as The Joy of Gardening and Charlie's Garden Army, as well as presenting coverage of the Chelsea Flower Show. In 2004, she appeared in the Channel 4 reality TV show, The Games. She has also appeared on American television, presenting a gardening slot on The Early Show on CBS. In September 2006, she appeared on the BBC's Celebrity MasterChef.
She has also published several gardening books, including the BBC Ground Force books Water Garden Workbook and Container Gardening, as well as Enjoy Your Garden, a book on general gardening published in 2000. Dimmock wrote a weekly gardening column in the Mail on Sunday for many years, until January 2008.
In recent years, she has enjoyed some success with a local ITV Meridian series, River Walks, in which she walks along various rivers in Southern England, visiting landmarks and attractions along the way, as well as meeting people who live and work on the rivers. The third series was broadcast on ITV1 Meridian in January 2008.
Dimmock was also the President of the Television and Radio Industries Club (TRIC) from 2003 to 2004 and presented their annual Awards ceremony that year. In 2011, Dimmock joined the team of experts on ITV's Daybreak breakfast magazine show acting as gardening expert.
Dimmock was scheduled to appear in pantomime over Christmas 2011 at the Spa, Bridlington playing the Organic Fairy in Jack and the Beanstalk. She returned to this role in December 2012 at the Pomegranate Theatre in Chesterfield. In 2013, she presented an episode of Great British Garden Revival.
In 2003, Dimmock competed in the Macmillan 4x4 UK Challenge charity event, raising the profile of the event considerably, which has gone on to raise over £100,000 each year for Macmillan Cancer Support.
She has also been involved in many other charity works, such as Dreamflight, a charity organisation for children with serious illnesses—that takes them to Florida, USA, for a "holiday of a lifetime".