Reform, despite pretending otherwise, is essentially a continuity UKIP/Brexit Party (essentially a Farage vehicle, I guarantee that some who voted for them will be confused as to why he’s not PM now) with the dregs of the Tories thrown in for good measure. Many of the problems they whine about can be traced directly back to their current MPs one way or another. They are firmly part of the Establishment that they claim to be against.
The Greens are picking up the left wing voters abandoned by Labour and the Lib Dems are a good fit for the the ‘one nation’ Tories similarly abandoned by their party. Both abandoning (some of) their base in pursuit of people that will never vote for them, or at least never will again.
On Manchester, the time for Burnham to return to Westminster was the last General Election. There’s no guarantees anywhere now and it’ll reek of a stitch up. He seems a decent enough bloke but trying to parachute him in as a PM replacement now is desperate. Perhaps a different story had he already been there.