If Reform get in with a hung parliament situation and the opposition being almost entirely left wing then he's ****ed. There's no way that party is going to manage that fiasco, you need seasoned vets in there not a bunch of chancers, the gov will just collapse.
Especially with FPTP, as you don't have another party involved to help you out. If Labour can squeeze enough seats to achieve a supply and demand agreement with the Liberals they will probably manage a term.
It's a similar situation to what's happened in Cornwall council. Reform won the majority of votes, but not enough to win the seat outright. They had two weeks to try and form a working council party and they just fell out with all of the other councillors because their plans were unworkable.
So the Lib Dems formed a minority council with a coalition from Labour and Tory councillors. Reform have a say on that council, but they were simply unfit to lead it
This is the reality of Reform when they are voted in. All mouth and no actual workable policies.