I have dealt with similar cases regarding Universal Wealth Preservation.
My clients haven’t wanted to ‘undo’ the arrangement (their intention behind the trust remains the same) but they have wanted to remove the Directors of UWP as Trustees. The Land Registry have been accepting a Deed of Removal and a subsequent Deed of Appointment of Trustee. I have then been sending a cover letter with the AP1/TR1 to explain why I have been unable to obtain the Directors signatures. It has worked in all cases.
Your particular case may be different if a charge has been lodged against the Title. I have spoken with other Solicitors who have said that their clients were unable to pay the legal fees up front so a charge in favour of UWP was lodged instead.