I need a mediator to settle a dispute between two directors over expenses

I am a 50/50 shareholder in a UK ltd company and I need someone able to resolve a issue over unpaid expenses for me. My co director has refused to authorise payments to reimburse me for expenses. The amount owed is 30k and he has offered to pay 20k but with strings. I started an employment tribunal case but want to resolve it sooner than May. I envisage you either meeting with the Director in London or by phone to put my case to him. My presence only agitates him and he can't think rationally.