12. Where any fee is to be assessed on the reasonable cost to the Executive of carrying out any work or testing under regulation 2(3)(b) or 9(9) or to the licensing authority of carrying out any work pursuant to regulation 9(2), the Executive or, as the case may be, the licensing authority shall on receipt of the application first prepare and send to the applicant an estimate of that cost and shall, before carrying out the work, obtain confirmation from the applicant that he wishes the work to be carried out on the basis of that estimate of cost.