ceases to make or have the intention of making supplies within sub-paragraph (2) of that paragraph; or

makes or forms the intention of making taxable supplies, shall notify the Commissioners of that fact within thirty days of the day on which he does so F2unless, in the case of a person ceasing as mentioned in sub-paragraph (a) above, he would, when he so ceases, be otherwise liable or entitled to be registered under this Act if his registration and any enactment preventing a person from being liable to be registered under different provisions at the same time were disregarded..