A visit to Alan's and it appears the offside driveshaft could be the source of the clunking. There was a bit of play between the CV and the shaft; turning the CV slightly didn't move the shaft immediately.

Either way the joint and shaft have to come off for another look.

I doubt that the problem is with the CV joint as both the old and new ones behaved the same.

Next is to get recommendations on where to get a pair of custom made driveshafts...

On a happier note, we managed to sort out the rear alignment. Started out hugely toe out but managed to get it just toe'd in. There may be a small adjustment to be made but I'm going to let the suspension settle out a bit first before altering it again. I am now adept at suspension alignment using cotton string!