Reviewing energy suppliers

For historical reasons, the gas and electricity supplies to our old flat are split across OVO and SSE. My account with SSE has been migrated to OVO. My website login for both OVO and SSE has the same e-mail address. I have an activation link for creating an OVO account for my previous SSE account, which appears keyed to e-mail address, the effect of which is to add an a problem has occurred message when I log into OVO, which then shows me my OVO account information and no SSE information. SSE's old website just refers me to OVO. OVO have told me that they cannot yet merge accounts.

Neither OVO's nor SSE's customer service seems to think they can fix the issue. So, the effect of the migration appears to be an unfixable, intolerable situation wherein my OVO account is slightly broken and my SSE account has become inaccessible. I had been planning to switch to OVO after moving to the new flat. I am now inclined to see which other suppliers get reasonable reviews and do not insist on direct debit and paperless billing. As usual with modern web portal workflows, I wonder how this got past QA, though I suppose it is usually that the engineers are incompetent or the business people promised impossible delivery dates.