OK, sorted, and here's how it worked on mine:


Two 13mm short bolts needed - put one with a big washer through the ring end of a beefy ring spanner and tighten into threaded hole on crank pulley. Thread other bolt most of way into opposite edge hole on same pulley. Axle stand under open end of spanner - turn pulley anti-clockwise to lock spanner onto axle stand.

10 minutes total of direct flame heat onto 24mm crank pulley bolt. (Two lots of 5 minutes so as not to melt any seals hopefully)

Used 1 metre long trolley jack handle over breaker bar to slacken bolt - just finally suddenly came loose after enough heating.

Pulley was hot enough too so literally could be pulled off with gloved hands.

Cashback!!!

Many thanks to all who gave tips, used pretty much all of them in one way or another.