Cant really tell you the inside credit control procedure for security reasons, but not all accounts are able to leave some are lucky some or not. The rules are infact getting more harder than they used to be. To be honest all bills have gone up and most direct debits increased due to the price of wholesale gas / elec. When you first sign for a supplier they go off your AQ = yearly average usage, to which they normaly use the country average for your area, as you can apreshiate though people use gas and electric in different ways and some houses use more than others. Maybe worth you speaking to energy efficency about your usage. I would not advice ignoring it though as external debt collection action is always taken and they do reserve the right to disconnect your supply @ the cost of £190 and also may report to credit reference agency.
Closed accounts are always sent to baliffs in the end, I would also like to say not defending them as I hate them as much as you but it always says on estimated bills that you can call with a read