lever? I've got the tool in a bench vice and i'm using the frame as the lever
Success - sort of. With the skewer to hold the tool in place I can now use the larger tool. Unfortunately even though the lock ring is alloy it appears to be an alloy of emmental and gruyere so it stripped
The surprising news was that the drive side came out using the same technique, leaving the BB stuck in the other half. Nothing a large hammer couldn't fix.
So I've got a stripped locking sleeve stuck in the BB but I'll soak it in WD40 overnight and try and cut it out gently tomorrow. I'm a happy man