I was overdrawn by £1.23 for about 3 hours on monday. The result: £35 charge.
I've had similar problems with Halifax before, when new direct debits have came off unexpectedly and had 3x £35 charges in the one day/letter. All for about 40 quid overdrawn. I called them and had the first two removed but still had to pay for one.
Thing is, it's entirely your own fault and you choose to bank with them so don't really have a come back to the outrageous charges. I find that taking the tact of "I'm an idiot but these charges are killing me, can you help" usually gets the person on the phone to remove them.
I'd love to move from them but this would mean 3 different accounts, mortgage, insurance etc and I can't be fecked. The same can't be feckedness that results in me mismanaging my finances obviously.
I think TSB give you 24 hours from the point your account goes into the red to sort it out before they hit you with any charges. This coupled with a nice wee text or something would be perfect.