Just a quick update.
Putting the gear back on, holding the assembly in my vice and wiggling vigorously worked after a soak in PlusGas (There is no other penetration fluid and don't say WD40) haha. Thanks Mike, good suggestion.
As you can see from the attached photo the shaft is quite scored as was the centre of the bush.
I started gentle, cleaning with a fine wet and dry. That had an effect but didn't allow the bush to run clean on the shaft. So, having cleaned the shaft of any burrs and high spots I put the bush in the lathe and using a very small boring bar I reamed out the centre by a really small amount.
That had the desired effect and everything slid back together smoothly, with the addition of some horrible think black Moly grease it all works fine.
I say fine, I still intend to purchase a new shaft and bush when they are back in stock.
Thanks for all the advice, it really helps to think these things through with others.
Mick