“ Appeals to a tribunal. (1) Subject to the following provisions of this section, an appeal shall lie to an appeal tribunal with respect to any of the following decisions, that is to say— (a) any decision by the Commissioners on a review under section 15 above (including a deemed confirmation under subsection (2) of that section); and (b) any decision by the Commissioners on such review of a decision to which section 14 above applies as the Commissioners have agreed to undertake in consequence of a request made after the end of the period mentioned in section 14(3) above. (2) An appeal under this section shall not be entertained unless the appellant is the person who required the review in question. (3) … (3A) … (4) In relation to any decision as to an ancillary matter, or any decision on the review of such a decision, the powers of an appeal tribunal on an appeal under this section shall be confined to a power, where the tribunal are satisfied that the Commissioners or other person making that decision could not reasonably have arrived at it, to do one or more of the following, that is to say— (a) to direct that the decision, so far as it remains in force, is to cease to have effect from such time as the tribunal may direct; (b) to require the Commissioners to conduct, in accordance with the directions of the tribunal, a further review of the original decision; and (c) in the case of a decision which has already been acted on or taken effect and cannot be remedied by a further review, to declare the decision to have been unreasonable and to give directions to the Commissioners as to the steps to be taken for securing that repetitions of the unreasonableness do not occur when comparable circumstances arise in future. (5) In relation to other decisions, the powers of an appeal tribunal on an appeal under this section shall also include power to quash or vary any decision and power to substitute their own decision for any decision quashed on appeal.”