Marks and Spencer is four weeks ahead of schedule with its conversion programme for the 28 Iceland stores it acquired for £38m in January.

The retailer is converting four stores a week for the next seven weeks to its Simply Food format, according to director of food Guy Farrant. He said sales were "fantastic" in the converted stores. Stores that have come on stream this month include Upper Road, Belfast, and Honiton in Devon.

The acquisition formed part of a rapid expansion plan for the convenience format. There are 151 stores now with 56 due to open this year.

"There is lots of scope in areas in which the ability to do an M&S shop is difficult," said Farrant.

Expansion is coming from both a traditional approach of seeking sites on a target list and acquisition, which makes up half the growth this year. "If opportunities arise we will be in the frame," added Farrant. The ideal size for Simply Food is 10,000 sq ft, but the Iceland outlets average 6,000 sq ft and travel outlets are smaller. There are 22 Simply Foods in airports and rail locations and 13 on motorways.

"We are looking at multiple sites. For example, we have two Simply Food outlets in Victoria station but could have three. The second was 100% incremental space," said Farrant.

The nine-strong BP trial is still being evaluated, but Farrant said: "The next big opportunity will be in forecourts."

"We update on BP in the autumn, but before we push the button we want to make sure it delivers and that we can manage that number of stores. But it is doing well," said Farrant.

Meanwhile, reports suggest that M&S is planning an ambitious international expansion programme that could see it open 150 stores in three years. As well as its UK operations, M&S operates 150 stores in 27 countries, including more than 130 franchise businesses.