Your having a laugh, The more I look into this the more it becomes clear the GQ C.V's are well known for breaking, Even more so than the Toyota it would seem. The Toyota rear is known as pretty good, Granted not as good as a Nissan rear but will out last a GQ CV many times over.
Ive been looking into this a lot over the last few months and the choices worth considering are either GU front and rear, Or 80 series front and rear with Longfield front shafts and CV's.
The GQ CV's aint much bigger than the LR ones, Granted the rest of the axle is massive but theres little point in that when the CV is small. Even with uprated units its still not going to be any better than an Ashcrofted/ARB'd Rover axle although it would work out cheaper untill the Nissan CV breaks.
The std yota CV's aint great (as im sure Nick will tell you) but with Longs they are known to be pretty bom proof.
Gu Axles are very hard to come by, If you do find them they wont be cheap, They wern't sold much in this country but Yota's are everywhere. Yota axles are cheap and the Longfields will cost you roughly the same as a front ARB for the Nissan.