If you have a dispute with a Business Transfer Agent then the first step you need to take is to make a formal complaint using the company's Formal Complaints Process. If you can't find the process on the company's web-site then write a letter asking how you can complain about the service.
You MUST take this step. You MUST allow the Business Transfer Agent chance to settle a dispute.
RTA's Compalints Handling Policy circa Sept 2011 used to be found here - RTA_Complaint_Procedure
Detail your complaint in full, in a letter that you need to send by Recorded Delivery. Ensure that you write BY RECORDED DELIVERY on the letter itself, which should have your correspondence address on the top right, and the current date. The letter itself, not only the envelope, needs to be addressed to The Directors, and state the full address of the company. The heading should be COMPLAINT. Use the company's reference number for your property or business. Refer to the date of any letter that the company have written to you. ALL contact needs to be in writing in case you need it for evidence. Please do not rely on e-mails unless you can set a "read receipt".
If the Agent who visited you when you signed the contract misrepresented the contract, services, or anything else then detail this. If you feel that the businesses was incorrectly valued then detail this too. Note any relevant dates of correspondence or telephone calls.
If your business has been on the market for a while and you've had absolutely no viewings or feedback, ask for details of all the advertising that has been undertaken. Ask for details of all the people who have been given your business particulars and how they were made aware of your business. If the information is not forthcoming, do a SUBJECT ACCESS REQUEST under the DATA PROTECTION ACT.
You should also considering coming to a settlement with your Agent.