You don't need a guarantee to return a faulty item. The Consumer Rights Act 2015 gives you 30 days to reject something that's not fit for purpose and get a full refund. After that, the retailer has to repair or replace it. If they fail, you can claim a refund or price reduction up to six years in England and Wales, five in Scotland.
Most people don't use this because they think they have to deal with the manufacturer. You don't. The contract is with the seller. If your kettle leaks after three months, go back to the shop, not the brand.
Digital content gets the same protection. If an app or software you paid for is faulty, you have the same rights. And services now must be carried out with reasonable care and skill within a reasonable time for a reasonable price. That covers plumbers, cleaners, web designers.
One thing that changed recently: prepayment voucher schemes. If a company goes under after you bought a gift card or voucher, you can claim from your bank or card provider under chargeback or Section 75. Section 75 only works for purchases over £100 and under £30,000 on credit cards.
Keep receipts, but banks transcripts or screenshots of orders also count. If a retailer tells you to go to the manufacturer, you say no. It is their problem.
Paul