In 1986 Caudwell became aware of the first of the then new mobile phones and discovered that there were large profit margins possible, so contacted the American handset maker Motorola to see if he could do a deal.
With his brother Brian, in 1987 Caudwell registered Midland Mobile Phones as a mobile phone wholesaler, taking 26 Motorola mobiles at £1,350 each. It took 8 months to sell these 26 phones to local plumbers, taxi drivers and television repairmen at a price of £2,000 each. The company made a loss every month for the first two years of operations.
Developing from a small dealership to a wholesale distributor, however, turnover expanded to £13 million in 1991, making it the UK's largest independent distributor of mobile phones. Turnover increased from £13 million in 1991 to over £1 billion in 2000. In 1996 and 1997, the Caudwell Group was named the UK's fastest-growing company for two years in succession.
In 1999, Caudwell was appointed as the President of the North Staffordshire branch of the NSPCC, and became the regional representative for the Full Stop campaign. Of the appointment, he says: "I was initially approached by the NSPCC to sponsor a cricket match. As is my way I got stuck in, took the whole thing over and was determined to raise as much money as I could." He was inspired to help children because of this experience: "I went to one of the NSPCC's centres and met some of the children who had been victims of cruelty and sexual abuse and it really opened my heart to helping children."
Caudwell founded the charity Caudwell Children in 2000. It became a national charity in 2006, and as of 2016 Caudwell is the chairman of the board of Trustees. Of the charity, he said: "I wanted to make sure that every penny that was raised would be put to the best use and spent on the children that needed it. My family puts about £2 million a year towards Caudwell Children. In addition I put in a lot of my time and I do a lot of networking. [But] the truth is my fortune isn't enough to help all the children that need help." The charity has proved controversial because it promotes unproven and dubious health practices and has aligned itself with antivaccinationists. The National Autistic Society asked Caudwell's charity to remove claims from its website that it had the society's support.
Caudwell was married to Kate for 25 years, ending in 2001. They had three children. He then had a relationship with Violinist Jane Burgess, with whom he had a daughter. He was then in a long term relationship with Claire Johnson for 15 years, with whom he has a son, but it was reported in October 2014 that they had separated.
By 2003, the Caudwell Group employed over 8,000 people worldwide and was selling 26 phones every minute.
A bull market player by nature, Caudwell could see the end of the growth days looming. In 2003 he sold Singlepoint to Vodafone for £405m (then $648m). Caudwell completed the sale of the wider Business on 26 September 2006, when it was revealed that the Caudwell Group had been sold for a £1.46 billion to private equity firms Providence Equity Partners and Doughty Hanson.
In April 2010, Caudwell donated £2000 to Conservative MP Bill Cash's general election fund.
In October 2011, he made a "significant" six-figure donation to the Middleport Pottery (one of the last working Victorian pot banks in Britain) in Stoke-on-Trent, through The Prince's Regeneration Trust. In October 2012, Caudwell was one of three principal private donors for the London's Bomber Command Memorial Appeal.
Caudwell has been awarded accolades for his philanthropic efforts. On 8 December 2012 at The Noble Gift Gala, he was presented with The Noble Gift Philanthropreneur Award by Hollywood Actress Eva Longoria for his dedication to charity work.
Caudwell's intention – for which he has applied for planning permission – is to replace the car park with super-prime residential apartments and town houses described by him as being in the style of "grand Mayfair architecture". Caudwell has a rigid belief that completion of his iconic apartment block, in place of a multi-storey car park widely considered to be a blight on the local skyline, Audley Square could become a desirable living addresses and will represent the heart of ‘Mayfair Village’.