I won't have a Smart meter as I believe that they will also the ability to charge a variable (higher) rate when demand is heavier - or whenever they like.
That is utter nonsense. You sign a contract for either a fixed or variable tariff. They can’t change it unless it is in your contract.
Of course they can't changhe your contract, but they could very easily only offer variable tariffs to switch to once your current deal has expired - and hike the price of the existing fixed ones so that nobody would want to/be able to afford to stay on them without switching one way or another. This is exactly what countless young drivers find with their car insurance - they either agree to a black box which varies what they pay according to safety of driving/number of miles driven/time of day of driving etc or otherwise go on the 'standard' non-telematics policy that costs a load more even than it does with the black box.
Energy companies don’t make much profit on energy, if any. That is why the likes of SSE have offloaded their domestic supply arm. I say this as someone who has spent 10 years in the industry for both a big player and a small social enterprise energy company. All the taxes, regulations, distributions costs etc make it virtually impossible to make profit.
Fair enough if that's been your experience, but I used to get bills from Eon that broke down where your bill money goes (presumably to counter complaints of profiteering) - 'For every £100 you pay us, £X goes to the refinery/power station who sell it to us, £X goes on distribution costs, £X goes on overheads and admin, £X goes on investment in infrastructure, £X goes to social schemes like Warmfront, £X goes to the government in tax etc.' IIRC, they claimed that about £6 out of that £100 would go to them as profit - 6% on that colossal turnover isn't bad at all, especially when the likes of Tesco supposedly only make half of that. I'd much rather make 1% profit on Eon's turnover than 99% on my local corner shop's turnover.