Hi Andy
I used a hacksaw blade to cut the shaft between the flap and casting, tried to tap it out after grinding the shaft where it was welded to the flap but no good only managed to snap the casting on the counter weight .
After cutting through the shaft either side of the flap it was easy to tap out the bushes and replace, then fettle them untill the shaft rotated easily bearing in mind it'll tighten up as it gets hot.
The only thing I think may be reusable is the flap though I hav'nt tried to drive the old shaft out yet as I opted to replace it all with new parts from Chris.
Pic shows the amount of wear on the shaft and remains of the bushes, plus the two part counter weight