PIP pre-tribunal advice sought

I have appealed the mandatory reconsideration decision and will now need to attend a tribunal. Need help building my case before I go (date not given yet). Local disability bureau is overwhelmed and cannot help, my husband went to Citizens Advice bureau for guidance but CAB not much use.   Someone said SCOPE may be good to try.  DWP said I didn't provide evidence - would a GP letter to the tribunal service be of use?  Any advice on who to speak to and what would be appropriate to provide gratefully received.