The announcement confirms rumours of a buyout sparked by the north-eastern factor chainâ€™s rapid expansion in recent months.
In 2009, new branches were opened in, Derby, Nottingham, Peterborough and Coventry.
And in March, the company confirmed that its 46th depot would open in Leicester on April 6, 2010.
This will be followed by a new operation in Kings Lynn.
The company was formed in 1946 and has been in full Page family ownership since 1979.
It now operates 46 sites and employs 1100 people.
The transaction was led by Andrew Pageâ€™s existing MD, Mark Roberts, alongside finance director Mark Day.
Page himself will continue to be involved as chairman of the trading company.
This is the 12th investment from Phoenixâ€™s Â£375 million fund, which was raised in April 2006.
AP is Phoenixâ€™s second recent automotive sector transaction. It sold Nationwide Autocentres to Halfords in February.
Andrew Page said the deal would allow the company to achieve further growth.
John Rastrick, a partner at Phoenix, added: â€œWe see substantial further growth potential for the business and are committed to supporting the Company to achieve this.”
New bank funding for the deal was provided by HSBC, RBS and Lloyds TSB.