Never understood the opposition to Smart Meters.
They record what you use and you get charged for it! Whether or not they might over estimate what you use is irrelevant as it will just go towards a credit on your bill....which you may or may not wish to reclaim?

We are about a £1k in credit for the dual fuel bill but I'm quite happy for it to sit with them should anything untoward happen in my life.

I genuinely don't think the energy companies are "out to get you" by asking you to have a smart meter. It just saves them having to send someone round to check your meter every few months, and you from having to poke around in whatever god awful spider pit you have your meter to read it.