Hi Ian, I've got a poorly one of these in a bucket of bits, and yes you do need to remove the star wheel hub. On mine there is a 5/16 dia (approx.) taper pin right through the hub, but the stub of the small end was sticking out so I just knocked it out with a hammer and punch.

You can't see the through hole in this piccy, but it is a through hole, promise! What you can see is that the end of the shaft with the thread (of a sort ) in it which carries the return spring ia bout 5/8 diam, the end where the star wheel sits is about 3/4 diam, and is supported in a bronze bush behind the star wheel hub. The pinion is larger than the ID of the bronze bush, so it has to pass out of the hole the other side where the ratchet wheel of the return spring adjustment sits. Thus you've got to get the star wheel off the pinion shaft first.

There must be the far end of the taper pin buried in the paint – has it been filed back flush and filled/painted over. Got to be something there you can hit wiv an 'ammer.
Once you've got the pin out, the star wheel boss is a good fit on its shaft and will need persuasion to get it off. But off it's gotta come. I toyed with drilling and tapping a bolt hole in the centre of the hub so I could screw a "pusher" in, but managed to weasel it of with pry bars at the edge.
Unfortunately mine has got bigger problems – I bought it off a friend of a friend who was selling up for retirement, but on cleaning it down I found that the outer cast iron casing of the quill is cracked. Bother!

If I hadn't paid so much for it it would have gone for scrap the same day. As it is I'm waiting for a week's snow so I've got nothing better to do than remake it!
As if that's not bad enough here's the state of the spline –

Somebody had a good old scrunch up that day!
Oh, and of course the gears are on their last knockings – but I expected that and allowed for that problem when I bought it.

HTH, if you need any more pictures it's all in bits and you're welcome.
Simon