Land Registry - Complying with a Form M Restriction

markrowney

To Whom It May Concern
I am a freeholder of a plot of land. There is a neighbouring plot of land that is only accessible via a pedestrian right of way over my freehold land. The neighbour has just lost a planning permission application and we are anticipating that the neighbour will attempt to sell its land at auction.
As a freeholder, we benefit from the following restriction placed on our neighbour's land register:
"(18.07.2019) RESTRICTION: No disposition of the registered estate by the proprietor of the registered estate is to be registered without a certificate signed by the proprietor for the time being of the estate registered under title number [redacted] that the provisions of Clause 12.6.4.6 of the Transfer dated 10 July 2019 made between (1) [redacted] and (2) [redacted] referred to in the Property Register have been complied with."
I understand that this is to ensure that certain positive covenants given by our neighbour to us under the Transfer, transfer to bind their successors in title with any disposition of the neighbouring land.
However, I do not feel that those covenants are sufficiently detailed to protect our interests. For example we can charge a service charge for the use of the right of way, but it is not clear how much we can charge. 
You can see that the restriction is recently dated; the Transfer was between the previous freeholder of our land, and our neighbour. There have been no changes to the nature of the neighbouring land since the restriction was given. It is essentially undevelopable because of the access problems; the refusal of planning permission simply confirms what most, but sadly not all, can see with their own eyes from the land itself, or from any of the legal documentation associated with it. 
Am I under any obligation to provide such a certificate if provided with a deed of covenant that complies with the restriction by a potential buyer? Can that buyer/our current neighbour take steps to either force compliance or remove the restriction? If so, can they seek recourse for their costs against me? Or given its recent nature, is it simply the case that I can prevent registration of any disposition should I wish to do so? I note that the Form O restriction speaks to 'consent' and not a 'certificate' suggesting that my discretion is not absolute. 
Kind regards
Mark