Why is my electricity bill �180 for 7 weeks?

I'm sharing a flat in Manchester and we're on the economy 7 E-ON tariff and our electricity bill for 7 weeks is �180. We use 2 storage heaters which are meant to charge up overnight when it's cheap with occasional convection heating. The boiler is meant to heat our water overnight too but seams to be making noise during the day too. Is this normal for economy 7 or could the boiler/timer be broken? Is there a possibility the storage heaters/boilers could be charging during the day too?