Whatever happens you should be able to check your own meter readings and your bills do seem rather high.
If as you say your landlord pays the main bill then re-charges you accordingly, as tenants/owners that should still give you the right to approve supplier especially to make sure they are not a "business" supply which can charge 17.5% VAT, and if you do all have individual meters why can't you each choose your own supplier?
Also worth checking
Energywatch to see if they have any information.