Trigger,
To be honest I've found their Direct debit to be as erratic as their service. For example they took less than EUR 30 from my bank account this month, even though I'm set up on 2MB which should be 59 lids a month.
Perhaps they are only charging me for days when the service works
However if they aren't keeping an eye on the money side of the business I'd be concerned that they might not have an eye on contention issues - I saw one post here about Skytel where the guy had worked out his contention ratio on a 14:1 advertised contention was actually nearer 24:1 (which would make sense in my context).
I'd suggest phoning them and asking them to confirm that they've taken the money. they will appear on a bank statement with the wonderfully cryptic reference "nnnnnn DD" , where nnnnn is your account number on the first invoice they would have sent you.
I'm looking into permanet a bit more closely now... if only to have a back up plan.
Interesting you had to get a Fixed IP as well - that was the first step I had to take with them to get the connection working as there was another operator in the castlebridge area who seemed to be interfering with their service (or so they said). Fixed IP suited me better anyway.