I contacted Mick's M&G people last Wednesday, and they responded very promptly to advise that the order had been cancelled and refunded, and to allow 5-7 working days for the refund to be reflected on my card. So, I'm giving them until the end of this week, otherwise it will be another email and contacting the bank to get them on to it.
In fairness to the M&G organisers, I suspect that they may have had to wait for their refunds from Ticketek/Ticketmaster before processing ours...
Or maybe I'm just feeling uncharacteristically generous today
