maybe a silly question, here's the setup:

I have a high end '85 Peugeot. The seatpost is fused with the seat tube. I know this because when trying to remove it, the single nut at the end of the tightening belt fell into the seat tube, where it now rattles and slides back and forth when I flip the bike upside down. I can't remove it because the seatpost and seat tube think that they are the same piece of metal. It is quite annoying.

Now, what I'm wondering is if I can get it out by removing the bottom bracket (which could probably use a cleaning anyway) or if the bottom bracket shell is a solid tube with the other parts welded or lugged onto it. Any ideas?