So are you saying that if

- YOU had disabled the password reset, and
- YOUR service were down, and
- you were communicating with me via email (possibly from a
different email address to the one in our database)

YOU would not want me to reset your account password based on an
image of a utility bill, but would insist upon a government ID that
I recognise?

Well my concern with a utility bill is that they're reasonably easily faked… it's not hard to do a Google Image Search for "gas bill", then edit the relevant parts in your favourite image editor.

Also what would be your suggestion regarding government IDs that I
don't recognise (not all customers are from the UK)?

I have to admit I'd not considered the non-UK side of things. That would definitely be a problem with the approach I'd suggested, as it'd be unreasonable to expect you to have an encyclopaedic knowledge of every possible government ID out there!

Perhaps if, at the time of disabling password resets, a customer was required to send in an image of a government ID that you could keep on file and validate against, in case they ever did lock themselves out? I'm not sure how happy people would be to do that, though.