New-car deliveries in the U.K. grew 10.9% in August to 65,937 units, bucking the traditional slowdown ahead of September’s number-plate change when about 17% of the year’s sales deals are signed.

August was the 18th straight month of industry gains and the fifth successive month of double-digit growth.

Newly installed Society of Motor Manufacturers and Traders CEO Mike Hawes says August deliveries drove the year-to-date market up 10.4% to 1,391,788 units.

“Private and fleet buyers are clearly capitalizing on attractive deals and new technologies against a backdrop of increasing economic confidence,” he says in a statement. “Ahead of the September plate-change, August always has far fewer registrations, but the 10.9% rise bodes well for the new plate.”

September typically is the second-largest vehicle sales month of the year after March, and in 2012 accounted for 17.6% of the annual market. SMMT says deliveries with the new 63-plate next month are expected to exceed year-ago’s 359,612 units by more than 7%.

The Ford Fiesta was August’s best-selling model with 3,289 units, giving it a market-leading 75,418 through the first eight months.

The Ford Focus, with 2,225 deliveries, dropped to fourth place in August behind the Vauxhall Astra (2,428) and Volkswagen Golf (2,233), but held onto second place year-to-date with 57,129.

SMMT says commercial-vehicle sales also were robust last month, climbing 14.8% to 13,451 units, up 7% to 190,159 for the year. Van deliveries rose 11.1% to 10,344, giving the segment an 8-month total up 9.4% to 161,938. Truck demand surged 29% to 3,107, leaving the segment’s year-to-date performance down 4.8% to 28,221.

SMMT Commercial Vehicle Manager Nigel Base says the CV industry can take heart from a respectable performance for the month. “For vans, August is always a quieter month ahead of the September plate-change, but the 9.4% year-to-date rise in volumes is set to be maintained through to year end.

“We predicted a turnaround in truck fortunes through the second half of this year,” he adds. “The robust performance in August is a signal that volumes should catch and pass 2012 totals.”

Ford stretched its new-car sales lead and share with 8,940 units, up 10.5% from year-ago. Through the first eight months, deliveries rose 11.8% to 197,933.

Ford CV sales also grew, up 5.7% to 44,823 units. The Transit van not only was the segment’s top-selling model, but also was the U.K.’s third best-selling vehicle, ahead of most cars.

Ford of Britain Chairman and Managing Director Mark Ovenden says the auto maker’s growth continues to outpace the industry. “It is significant that private customers have driven up our share of more-profitable retail sales, which account for a higher proportion of registrations in the important September sales month.”

Mercedes-Benz U.K. says it saw an “incredible” August with 3,028 deliveries for a record 4.6% share. Sales through the first eight months hit 64,779 units for a best-ever 4.7% share.

President and CEO Marcus Breitschwerdt says the German luxury brand is winning record numbers of new and returning customers in the U.K. “In addition, there is encouraging growth in the commercial-vehicle market, and our order banks are looking strong for the coming months,” he notes.