Russell - The forms that you have mentioned are the correct ones to complete for removal of the restriction on the title. There is no standard wording that I can suggest. It is for you for the applicant or their legal representative to tell us how the interest protected by the restriction has come to an end. More information on this can be found in our
Practice Guide 6.
With regards to the basis on which the restriction was entered on the title, it would have been done as a result of an application submitted to us. You can query how that happened and obtain a copy of the relevant document. If you wish to do so then I would suggest you contact our Customer Support using the Contact form on our website in the first place - https://www.gov.uk/guidance/contact-hm-land-registry