Well no one replied so I did it anyway, so the answer is yes you can do it this way.
I was worried it would not go back together, but it did.
I put car on axle stands, undid the 4 bolts holding on the inner wishbone mounts, I undid the CV boot clip, pulled the boot back off the inner cup, then just yanked the whole lot outwards, with a bit of tugging I got the shaft to come clear out of the cup, then removed the clip off the driveshaft end and slipped the spider of the splines.
Slipped the new spider on, made sure the clip was back in place in the grove and adjusted the boot so it lined up, then pushed it back together, wouldn't quite go back in as inner arm mount was slightly too low so used trolley jack to lift arm slightly then pushed a bit more then lifted slightly and pushed a bit more, till joint was fully located.
Pushed lots of fresh CV joint grease in and fitted new clip.
Put outer bolts in but didn't tighten, wiggled into best place then tightened enough so inner bolts could go in then tightened all bolts, and jobs a good'n, took about half the time of "correct" method and as no ball joints have been split no fear they have just failed in middle of the job.