It's not too bad because it all evens out at the end of the year. For instance, they just wacked our monthly DD up quite a lot b/c we just had a high meter reading for last quarter (all the cold weather). So to make up the deficit, we're paying more per month for the next quarter. After that meter reading in 3 months, the rates will go back down again to adjust for the lower usage coming up in the summer. Does that make sense? I think you just have to make sure you're giving prompt readings and not letting them get away with estimated bills. Also, you can at any time phone up and ask them to reduce your monthly DD and cash-pay the deficit separately.
When we 1st set up the acct, they wanted to set our monthly DD at something quite high, so I just called and said we had been paying £xx with our previous company, can we start off with that and see how it goes? They did it, no argument.