Well, just as I was about to leave work today, one of my colleagues more or less took the bike out of my hands. Into the workshop we went, found a 1/2" dia. piece of mild steel bar, ground on chamfer on the end and knocked it in between the split sections of tube. He then told me to operate the vice, so I did.
There he was swinging the frame around gripping on less than 10mm of broken sections of tube, and lo, it moved! Then some more! And then out she came!
I had to file the rust out there was so much in the seat tube!
All I need now is a new seatpost and some grease...