If they had an incorrect address but correct meter details and sent bills there then they are covered.
If they had tried to get meter details or reads then they are covered.
If they have made no attempt to get meter details or reads and no bills have been sent out then the billing code applies IF you had made an attempt to register with a supplier.
Basically you have used the electricity and must pay for it.
You MAY wangle an exgratia payment out of BG if you cause enough fuss.
Unfortunately for you no attempt was made to contact them when you moved in, therin is your downfall.
With my company if no payments made for a year then a PDV (pre disconnection visit) is performed to find out who lives (or if property unoccupied) at the property. Depending on the result certain things happen. Most bad, ie pre-payment meter installed with the debt set on it to be repaid at usually £10pw or if unoccupied the meter will be removed. In this country every property has a right to supply (elec not gas) and every property in the country has a supplier. You have the right to change supplier which this site is all about but that changeover takes about 28 days so even if you contacted a supplier when you moved in and they took over the supply you would still have owed BG for the first 28 days.
Let me know if you need more info but going to Energywatch ( which will be disbanded in Sep08) won't do you any good.