The most affordable motorway service station for petrol in the UK is in Wales. Moneybarn analysed fuel prices, finding Magor services at M4 junction 23A as the cheapest, with petrol costing 139.36p per litre on average. Rising petrol prices are a concern for UK drivers, with searches for reasons behind the increase surging. The RAC claims drivers are paying too much for petrol and diesel, with retailers allegedly overcharging. The findings aim to help drivers save money while refuelling on the road.