The Legal Ombudsman has issued Guidance from with case studies, setting out the types of issues involved in these cases, and how they're likely approach them if they were referred to them. Although mention is made early on in the advice about success fees, the guidance is of general application to all costs complaints and is helpful. Core to this is setting out at the beginning in your retainer documentation (letter of Engagement or Client Care letter) what the client will be paying and when and coping the work. There’s no way to avoid that. Its basic contract law.
Here’s the link to the guidance (issued in the autumn of 2024): https://www.legalombudsman.org.uk/for-legal-service-providers/learning-resources/preventing-complaints/complaints-about-legal-costs/
