Hi, I am still trying to find the Tenancy agreement but not sure I have one.
The deed of covenant you have shared makes reference to a lease dated 26th April 2006, so one must exist.
From what we've seen so far, in the absence of any clause/covenant in the as yet unseen lease, the space is yours to use, and there's nothing requiring you to allow a third party parking company, a stranger to said lease, to issue charges in your space, and much less for you to enter into any contracts with them/pay them any money. Any appeals to the parking company can be made on this basis - you may wish to share a draft here for feedback.
Any correspondence with the management company will be along similar lines - although getting a copy of the lease would be wise. Then you can refer to that and all the documents and make clear that there is no requirement for you to participate in any private parking company scheme, nor allow them to operate on your parking space.
You may want to read up on cases on PePiPoo and the MSE forums regarding residential parking, and 'primacy of contract'.