Frank Erskine wrote:

Of course the reality is that all their charges/tariffs are so
volatile that choosing a "best deal" today may become horrendous
almost tomorrow...

Some of the 12 month fixed price deals are only marginally more
expensive than the current price of 12 month additional discount deals,
the energy companies seem to be sending out scare stories for next
winter already, presumably based on forward prices they're negotiating?