I think it unlikely that Octopus Energy will fail in the UK. Octopus are a multinational company that also generate green energy themselves.
Customers from some of the small UK energy suppliers that have failed have been transferred to Octopus Energy.
Octopus Energy are also actively recruiting the skilled staff from these companies that have failed. This is a golden opportunity for Octopus to expand.
Once you are with Octopus Energy you can easily and quickly switch to one of their tarrifs that suit you.