Seat believes the three-door version of its Leon, the Leon SC, could take up to 25% of total sales of the model range with conquest sales from rival manufacturers.
Neil Williamson, Seat UK brand director, said: “We've taken advantage of our opportunities when they have come along.
“We are very strong in the retail sector where most of the growth is coming from, and the dealers are very focused on that. This year our growth is almost double that for the market as a whole."
The European market is proving difficult for Seat and many other brands. However, its UK performance is up 18.6% for the first six months of 2013, with 22,752 registered so far this year.
Williams believes the tide of payment protection insurance compensation claims has helped the UK to buck the downward sales trend, but is not the only factor.
"To some people PPI has seemed like free money, although it's not been a huge driver. The main thing is that the economic indicators in the UK - house prices, unemployment levels, GDP and interest rates - are starting to look better.
"Consumer confidence and business confidence are moving up quite nicely."
Seat has one of the youngest customer profiles in the business, with an average age of 38, and the Leon SC is expected to resonate with the company's typical buyers and open up the brand to those customers looking for a three-door.
"Our DNA lends itself to a three-door," says Williamson. "We've not been able to offer one before. Now we can."
The SC is shorter and lower than the five-door Leon and there are three trim levels - S, SE and the lower and sportier FR - priced from £15,370, which is £300 less than the corresponding five-door.
The five initial engines - 1.2- and 1.8-litre petrol turbos and 1.6- and 2.0-litre turbodiesels - will in time be joined by a 1.4 unit which shuts down two cylinders when cruising to save petrol, and an ultra-low emissions, ultra-high economy 1.6 diesel.