Right chaps, an update. I didn't realise that the distance clamps actually turn independently as they aren't internally splined so with some tapping they knocked round and the clamp bolts could then be removed.
Unfortunately I'm really struggling to get the drive sleeves into the transfer box to slide back into the centre bevel boxes, they slide backwards and forwards easy peasy in my reconditioned bevel boxes I have to fit, unfortunately after 25 years in a field the ones on the truck aren't so easily moved!