[Normille]

If you've signed up for a payment plan for £xx/month and overnight it goes up to £xx+30%/month in August, with the threat of another similar price hike in January, it could be argued that the energy companies broke the contract.

Yes, there has always been the possibility of prices rising. But there's also always been a reasonable expectation that any price rises would be in line with inflation. Not +30% twice in the space of a few months.