I can sympathise with working out something yourself and it being wrong and then being stung and being upset at *yourself* BUT they’ve admitted not submitting readings, it’s only been so cheap because you’ve not been telling your energy provider your usage so far and now you have that usage/spend has caught up.
I’d say 115 per month for gas and electric is far more accurate for a house that size (in fact I still think that’s bloody lucky to still be so cheap, speaking as someone’s who was paying similar with monthly readings and who’s energy company has been one of those to go bust) than naively thinking you were only £80 per month.
You can’t blame that on the energy crisis!