What am I doing wrong

[Albus1971]

Give the top of the puller a couple of whacks with a hammer.
Or if you're not worried about damaging the horn wire, just undo the nut until there's a couple of threads left and give the nut a couple of whacks. This should shock the wheel off.
Works for me every time, I've never used heat, water or pullers.

Oh my days. This worked a treat. Left the nut so it was just proud of the shaft (oerrr) placed a 24mm socket upside down on top with small extension bar inside and whacked it with a hammer. 1st few tries and a couple of Bakelite bits fell off as expected. Was about to give up and thought try again. Gave it a few harder whacks and steering wheel came loose. Absolute star, thank you.