Lidl – along with fellow German discount retailer Aldi – is known for challenging Britain's 'big four' supermarkets – Tesco, Asda, Sainsbury's and Morrisons – in a bitter and long-running price war. But Lidl is taking it to another level, now challenging upmarket retailers like Waitrose.

The UK’s supermarkets are at war. With each chain jostling for space in a market predicted to be worth £203 billion by 2019, Waitrose’s Pick Your Own Offers scheme aims to grow the brand’s share with customisable discounts. But is it enough to win the battle for supermarket loyalty?

As people spend less time in traditional communities, they’re seeking connections beyond religion and family. Memberships with organisations or brands can create loyalty and boost revenues, but the reasons to join Scientology or Sainsbury’s are vastly different. So why do people become members?

In the wake of poor Christmas numbers, Chief Executive of Sainsbury’s Mike Coupe feels it would be “very brave” to predict improvement in 2015. Yet, while the big four report drab festive figures, it’s discount brands Lidl and Aldi who have cause to celebrate.