It expects to increase profits further with retail acquisitions and partnerships planned for the next year.
Pre-tax profits at the firm for the six months to June 30 were up from £30 million to £52.5 million.
The firm said confidence had returned to the car buying market, with retail profits up 21.8% to £6.7 million, while leasing business 'improved slightly' over the period. Expectations on residual values were being met.
It revealed that online transactions were not growing as originally anticipated at internet sales site Autobytel UK, but said losses had been 'significantly reduced'.
Chief executive Peter Johnson said: 'In the UK, our partnerships with BMW, Toyota, Lexus, Audi, Jaguar and Land Rover are driving outstanding earnings growth.
'We have added to our portfolio in the first half and I expect this expansion to accelerate in the second half.'