Hi, just follow up - was contacted by 'RB' who was very helpful - and as good as his word a cheque arrived to refund the money that had been taken from my Direct Debit. You cannot believe just how relieved I was to FINALLY sort this out and talk to someone who actually did what he said! So full marks to 'RB'

and nil points to Customer Assistance.
Case over so I hope my pulled-out hair will regrow! (...and of course that I don't get another bill in the post next week....)
THANKS RB AND CABLE FORUM GUYS!!