The Commissioners may from time to time, on application to be made by the landowner, and after such inquiry as they shall think fit, sanction any modifications or alterations either of the scheme of the improvements or of any other matter expressed or referred to in the provisional order: Provided that no such modification or alteration shall increase the sum to be charged in respect of the improvements, or extend or curtail the term of repayment, beyond the greatest amount which it was proposed so to charge, or the greatest or least term over which it was proposed that the rentcharge should be spread, as respectively stated in the . . . F1notices herein-before required: Provided also, that every such modification or alteration shall require the consent of every party who, by having contracted for the execution of the improvements, or by having taken an assignment of the title to an absolute charge, or otherwise, may be interested therein; and the modifying order shall be in such form as the Commissioners shall from time to time appoint, and shall be construed together with the original order as one order with respect to all rights arising thereunder after the date of the modifying order.