Dzug - I don't see how anything related to planning consent can get onto a Charges Register.
Isn't it more likley that the original seller of the land wanted to benefit a family and not have some Victorian property developers sell on the plot? If so, it is only the original seller of the land (or maybe his successors) who can invoke the restriction in the Charges Register - and that is pretty unlikely.
I wouln'd worry Martin, though it is possible to buy indemnity insurance to 'cover' one against such an outcome occurring.