UK cheapest supermarket revealed as Which? has revealed the cheapest supermarkets (Image: Getty)Aldi has been crowned the cheapest UK supermarket again in the latest Which? This was £1.18 cheaper than rival Lidl, where an identical shop came to £123.95 on average. ‌Waitrose was the most expensive on average, with the smaller shop costing £161.19 on average and the bigger shop costing £531.39. Retail Editor, said: “Aldi is the UK’s cheapest supermarket again this month, according to our latest price analysis, showing that it continues to represent great value without the need for two-tiered pricing.