Start by complaining to the trader in writing, explaining the problem, the remedy you want and giving a reasonable deadline for a response. If this does not resolve the issue, contact Citizens Advice consumer service in England and Wales, Advice Direct Scotland or Consumerline in Northern Ireland for guidance and possible referral to Trading Standards. You may also be able to use an approved Alternative Dispute Resolution scheme or an industry ombudsman; check the trader’s terms or GOV.UK for the correct route. For complex or high-value disputes, consider advice from a solicitor regulated by the SRA.