" . . . a sentence imposed, or other order made, by the Crown Court when dealing with an offender may be varied or rescinded by the Crown Court within the period of 28 days beginning with the day on which the sentence or other order was imposed . . . "
"Where a merely formal variation in the sentence is made after the expiration of the time limit, which does not alter the substance or the penalty, but merely cures an irregularity in the order of the court, the amendment will not be invalid."
"On an appeal against sentence the Court of Appeal, if they consider that the appellant should be sentenced differently for an offence for which he was dealt with by the court below may -- (a) quash any sentence or order which is the subject of the appeal; and (b) in place of it pass such sentence or make such order as they think appropriate for the case and as the court below had power to pass or make when dealing with him for the offence; but the Court shall so exercise their powers under this subsection that, taking the case as a whole, the appellant is not more severely dealt with on appeal than he was dealt with by the court below."