and ..... Success !!
Both inner races successfuly installed in the steering head
Initially I partially tapped the races into the frame using a copper mallet, just to get them aligned nicely, then fitted the compressor and applied the impact driver, they just popped into the frame.
Afterwards, I removed the compressor and using the old race I tapped with my mallet just to make sure I got the metallic ringing sound
Having done it, I would say that it is probably possible to achieve this using only the following :
1) Old race with cut in it
2) Frozen new races
3) Heated frame where races fit
4) grease where races fit
5) Mallet
The compressor was not essential but did make it very easy. The grease bearings (two washers with lithium grease in between) worked well (prevented the nut turning the old race), the wooden centering spacers not really necessary, I did also use a long bar on the socket to do a final tightening of the compressor but didn't get much further than I achieved with the impact driver.
My plan is to use the compressor on the inner race but that will be a week away, need to wait to get the stem back from the blasters
Thankyou to everyone for your pointers, helped enormously