Mercedes VT form signing

[sildenafil31]

I VT'd my Mercedes in September 2019 and was sent an invoice to pay for the excess mileage on it a month later. It was approximately 5000 miles over with a charge of just over £600. My file is currently with DLC and they have now sent me a letter to say it will be passed on to the solicitors Mortimer Clarke.
I am happy to dispute this charge, having read the guides on this forum, however I made a mistake at the time of doing the VT in that I signed the form sent to me by Mercedes which said I was liable for any damage and excess mileage charges.
I was wondering if anyone else had any experience of signing this form and still being able to dispute the charges or whether because I have signed it I will fail if it ends up going to court; something I would obviously want to avoid if it ever gets to that.*

I appreciate any help you can give.
*

[sildenafil31]

Please can anyone advise me on whether signing the VT form which stated that I accept any excess mileage charges, would override the CCA and mean I would be liable for these charges no matter what argument I put up against it.

Thank you