Honestly, you might be partly to blame. Escalate anyway.

You messed up a bit, but the company's own failure turned a small problem into a disproportionate one. Give it what went wrong on both sides, and it writes an escalation letter that admits your role in one sentence, then pivots hard to their failure and the remedy you want. It flags how the Financial Ombudsman weighs proportionality.

Write an escalation letter to [company name] where I accept partial responsibility for [brief description of what went wrong] but argue the company's own failure [describe what the company did wrong] made the outcome disproportionate. Do not over-apologise. Acknowledge my role in one sentence, then pivot to their failure and the remedy I am seeking [desired outcome]. Flag that the Financial Ombudsman considers proportionality and contributory fault when assessing complaints, so shared blame does not end my case. Tone: honest but firm.