I didn't want a smart meter, but . . .

[Geek]

They would not accept my readings, but instead relied on obviously wrong, mutually contradictory, readings they kept changing in the metering history on their system.

Worth clarifying that they were not adding the replacement incorrect, readings to the meter history. They were overwriting readings in the history, then emailing replacement bills with different charges but the same invoice number and date. Basically fraud.
It turned out that both the gas readings and the electricity charges were wrong, fordifferent reasons.
My photos and spreadsheet ended up being the only reliable record of what had happened.
The more we rely on 'smart' and 'cloud', theore vulnerable we are.