“A declaratory judgment is a discretionary remedy, and it is true that in the ordinary case the Courts will not grant a declaration in favour of someone who has already obtained one, but it has been held in this Court on a number of occasions that where the subsisting declaration was not tied to a plan of the land, and is not accepted by the defendant as binding, that may be a good reason for the Court’ s exercising its discretion in favour of granting a more effective declaration by reference to a plan.”