The petrol and diesel prices are sourced from Experian Catalist (www.catalist.com). The sample is made up of 28 supermarkets and 49 non-supermarket sites. The non-supermarket sample is reflective of each brand’s market share and accounts for the range of different franchises and unbranded retailers. All prices are correct and accurate as supplied and for a date within the surveyed week. * means that only one retailer has been sampled in that area during the course of the week.