Millions are voting for them and they could grow a fair bit more.
Being realistic, a lot of the labour votes were just a vote against the tories because it was a shitshow. If Labour don't show clear improvement from the tories, then I wouldn't be too surprised to see another rise in support for Reform.
I know plenty of people who voted Reform, people who I'd never imagine would be voting for a party spearheaded by Farage. And we're not just talking "gammons" as some like to say, I know a pretty diverse mix of people that voted them.
I voted Labour personally, not with a great deal of confidence though, and i think that's the case for many.