Gonzy, a screwdriver behind the cranks and a hammer. 😆
You’ve obviously not experienced properly seized cranks before. These took ten minutes with a lump hammer even once the taper was 1/4 exposed.
If the stem is rusted to the steerer I assure you undoing the top headset nut will achieve the grand sum of sod all. It’s ok, I know what I’m doing…
Sentimental value? Not really, it’s a £7 eBay cannondale M500, I’ve got half a plan to cobble a commuter together, but mainly I don’t like being beaten. 😈
The bottom bracket was exactly as awful as you’d imagine but I got it out in one piece, not sure how you’d even go about getting that out without ruining the frame of it was completely seized.