Get yourself a spreadsheet setup with a simple lookup table for the tariff rates ie Day Night Standing Charge and VAT like this
and take monthly meter reading and enter them each month!
Its the only and easiest way to work out your energy useage
I have a large 2 bed flat and electric sotrage heaters on E7 and use less than £50 a month but all my bulbs are led low energy and i have trimmed all my energy useage down - only use hot water when i have a bath as i have a vented cylinder boiler - who says modern combi boilers are great are mad - the old 60’s boilers save far more leccie.
Smart plugs control all the lighting and tv etc and i still use less than £50 per month
You cut your cloth to fit your pocket