Same thing happened to me when I was putting in the new rack. IIRC I had to remove the steering wheel, and let the whole steering column slide down, then I hit the UJ from inside the engine bay (through the hole in the bulkhead), after a good few bashes, lots of swearing and a few drops of blood, it went onto the shaft, and I stuck the bolt through. Next difficult bit for me was pulling the steering column back up from inside the housing, I ended up putting the nut onto the spline section and levered it out, and held it very carefully whilst putting the steering wheel back on.
It was a nightmare, because when the column drops down, the bearing falls out of place, and the stupid spring at the bottom of the column just makes fitting the UJ near impossible. You really do need 5 hands to pull off this manoeuvre.
Hats off to the VW engineers on this one...