Congrats Steve, my Penelope was seized when I got her too. Not badly though. You can find out if it's the rings that are seized by taking off the head and gently rocking the flywheels back and forth. If it's the rings that are seized, the cylinder (barrel on your side of the pond) will move up and down. Mine and many like ours have the chrome worn off right near the top of the cylinder in a small oval area from the top ring to the top of the cylinder. That's where the rings seize. Mine came loose after a generous soaking in penetrating oil, then gently raising the cylinder by turning the flywheels, then gently bouncing it down. I stress gently as we are dealing with fairly fragile cast iron.
Anyway, if the cylinder doesn't go up and down with gently movement of the flywheel, don't force it, you need to take off the connecting rod and inspect the crankshaft.
stan