The discounter, which currently operates 196 UK stores, has pledged to open several this year, refurbish many more and totally rebuild others.
Accounts for 2009 filed at Companies House showed pre-tax profits well up despite sales growing by just 0.2% to £745.5m. Operating profits grew by 53% to £7.6m.
MD Charles Kay, who replaced Richard Lancaster in January 2009, hailed the results as "excellent".
"Continued control of costs, good relationships with our suppliers and more exciting marketing activities have given greatly improved results," he said. "This is a credit to our committed and professional colleagues. I'm very pleased with the way the business is progressing."
Profits were helped by the cost of consumables and raw materials falling £6.4m to £614.7m and a change in stock levels adding £2.9m to its income.
Kay called trading in the first four months of 2010 "extremely buoyant".
"We are trading up, attracting more customers and increasing their spend in our stores," he said. "We are planning several new stores in the coming months and will be continuing our extensive refurbishment programme."