After receiving estimated bill after estimated bill, and the ESB changing my direct debits more than 4 times in the space of 6 months (I'm on a monthly equalizer bill), I resorted to checking the meter myself. Then averaging out over the cost of the year what my ESB costs me. Then rang customer complaints and held them to the price that I reckon our ESB bill will cost us per month.
Funnily enough, it's worked and I haven't had a problem since and we're not owing them any money!