Warranties do not mean much, especially when it is as short as 90 days.
What is important is the Sale of Goods Act. This says that goods must be as described, satisfactory quality, fit for purpose and last a reasonable time. “Reasonable time” is not defined but there is plenty of case law and most goods are expected to last at least 12 months.
If the goods fail your claim is against the retailer (NOT the manufacturer, hence my remark that warranties mean little). You should ask the retailer to repair, replace or reimburse you (the choice is yours) and if you have difficulty your first port of call should be your local trading standards department who should advise you how to proceed.