This whole business of direct debits or standing orders scares me. I don't use them here (in the States) because I don't like the idea of not controlling when I pay the bill, especially since my payday isn't fixed. It seems that DD and SO are much more common over there, though, and in some cases required. My bf's rent is DD every week or month (whatever it is). It seems that the system is set up to force people to use DD even if they don't want to. This is all based on observation of what I've seen there and what I have read here.
The banks don't force people to pay with Direct Debit, the company who you are paying determines whether or not you can pay by means other than Direct Debits. The company are obliged to confirm in writing to you the exact date that the instalment will come out and the amount. They must do this a minimum of 10 working days before the first instalment is due.
Failed Direct Debits are represented by the Company you have the DD set up with, the bank is only doing what they have been told to do.
DDs can't be represented on an hourly basis. It takes a minimum of 3 working days to set up the represented payment (again by the company, not the bank). If a DD has been represented more than once in a business day then that's a fault of the bank and they should be forced to repay any charges incurred.
Standing Orders are entirely in your control.
In both cases, if you know that the funds aren't available you can stop the payment going out (and avoid any charges) by contacting the bank (any branch) as late as 5pm the day before it's due out to get it stopped.
In saying that...if a DD of mine bounces then I would want the bank to pay the instalment on my behalf to avoid any sanctions that the company may impose ( ie BT cutting you off)...but I don't want to pay £30+ for the pleasure.