i am in the middle of doing this at the moment mate i have used a seat tube of a cheap bike the same size i have a spare mk2 burner tube as well if thats the size of your tube
did a bit of work on my yammy frame yesterday
seat post was stuck 2" from the bottom
tryed heat the axesaw down the frame
resorted to new seat tube
the old post was able to hammer out with a 1/2" extention bar
see the axesawed all the way through still never came out :evil: