That's odd.
This time last year, I stopped getting bills. When I chased them it was because they were missing data. They'd retrieve it, and bill me. This happened 4 or 5 times until about May, when after the same process they didn't get it, and couldn't bill me. After weeks of chasing they admitted that the meter they'd fitted wasn't working properly.
They back billed me on a normal variable tariff, with the promise to sort it once the meter was sorted. To their credit 2 months later the firmware on the meter was updated, and the readings retrieved and they redid the billing correctly. Rather than billing me missing periods at a higher rate.
Unfortunately since then, I've also stopped getting Electricity bills. I can see the usage on their site, they just haven't issued bills. I chased just before Christmas and they've managed to catch up two weeks at the end of Sept... but nothing since.
I think they're a bit busy at the moment.