Sent a formal grievance to all parties involved today from advice from Acas and the agency inspectorate.
To my agency manager, agency directors, and umbrella.

Outlined I was unhappy with the service and ineptitude to do basic administrative tasks allowing the contractor to be paid.

I pointed the finger at the agency as my contract states they will pay the umbrella weekly.

Went through my emails from March last year when I had this trouble. Once they accepted responsibility and sorted the b2b contract. It was done and signed in 13 minutes.