As an incidental point, ukfsn itself has no staff.
Re the Entanet billing, your tale, (shocking as it is), confuses me a little.
The cancelling of the Direct Debit could be the cause of the final invoice to get rid of the credit owed, as without it is place their system will not be able to do the refund. It could of course be given with a manual payment using BACS, as they have your details, but perhaps that is beyond them.
My main confusion though is the billing itself. Unless Entanet have changed their accounts procedures in the last 12 months or so, they refund the unused balance from the migration date to the end of the paid-for period.
By the look of it your payment date was the 15th of the month. So you should have had a refund from 30 December to 14 January. The £9.68 refund looks like that.
So what was this "final 30 days" payment on 14 January, with which you seem to be content?