I am a solicitor but I appreciate we are all different and you happened to have been let down so I do not take offence.
The public access barrister will need your brief and the brief would need to request that they represent you to pursue a solicitor for professional negligence and you will have to list the documents that you are providing the barrister to review, in a bundle and in chronological order:
1. So you will start from the Appeal and the Order that required you to make payment of the £60,000.00 and this would state when the money was to be released and all correspondence that was exchanged with the solicitors with regards to the release of the payment to when the payment was actually made 8 months on
2. They will want copy of the file relating to the claim by the third party against you for the delay in releasing the funds and the court order or agreement that ended you with having to settled their damages and solicitors costs. If you were represented throughout this evidence of your own costs
3. Evidence of properties lost to fund the costs
You will need to see them face to face in conference once the brief has been sent to them. The Counsel will be able to tell you of any more documents they require
Once you identify the barrister you want to use when you speak to their clerk they will often tell you in any event what the barrister wants to see in the first instance