When changing all 4 UJs, I found that the easiest way is to take out two outer joints, take out the inner roll pins holding the drive shafts to the gearbox diff output shafts, take the driveshafts off the car, pull them apart on a workbench, assemble the shafts by pressing them together in a vice on a workbench, then putting the drive shafts back and only having to fit two needle roller races in situ on the car.
If the circlips won't go back in place in the yokes, it probably means some of the needle rollers have fallen down when you were bashing the cups back into the yokes.
Don't forget to get the grease gun on to the long grease nipples when the whole shaft is back in place. The nipples can only be removed and fitted if the driveshaft is horizontal, otherwise you cannot get the spanner (wrench) on to the nipple, and the hex faces on the nipple will foul the yokes as you turn them.
