Are there any places where you can, for example, just tank up and drive
off, and then later receive a bill in the post or have your bank account
linked to automatically take payment at the end of each month?

Um, anywhere that takes credit or debit cards?

Our local fuel company used to have a box full of locks and dials on
each gas pump. Each customer got a key, you unlocked your lock and
pumped, the gallons were counted on your dial, and he sent you a bill
at the end of the month. Then the owner retired, and they don't do
that any more.

It's the only place in the US I've bought gas at an unattended pump.
At places open to the public, fire regulations seem to require that
there be an attendant who can set off the fire suppression system.

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