Great intel;......
What does putting the handbrake on do if both back wheels are off the ground?
The part arrives on 18th so I’m free til then....
Thanks again...

Handbrake operates on the rear propshaft so it locks the props which prevents trying to turn the rear prop doesn't turn the front one.

Job done. That DA1065 tool I would suggest is essential to undoing bolts on the drive shaft from rear diff. I was able to access all 4 bolts on driveshaft without having to raise either front wheel off the ground. I used that same tool to access the nuts on the differential. I would recommend, I’m sure most would do this anyway, that you get a pointed object and clear all dirt and grime from around the diff nuts before attempting to remove them so as to allow the socket to get proper purchase on the nuts. I found a few of the nuts were heavily caked with grime and socket tool couldn’t fully enclose the nut.
When I had the driveshaft disconnected I propped it up in its highest position using a 2x4. If you allow it to sit in the lowered position while supported the differential will have very little space to fit the diff by the driveshaft when you are taking it off. WIth driveshaft raised there is plenty of room to remove the diff.
With all nuts removed I gave the diff a belt or two with hammer until it broke free. After that I positioned a trolly jack underneath the dif and took the weight of it from the bolts on diff housing. I then just needed my 2nd pair of hands (12 year old son) to slowly push the trolley jack towards front of vehicle while I balanced the diff on the jack. Once the unit was clear of housing the jack was dropped and diff removed. I did the exact same when reinstalling the new diff. I used all brand new bolts and Nylok nuts when reinstalling.
While the half shafts were removed I replaced both drive seals. Care must be taken when reinstalling the shafts not to rest them on the seals so as to avoid disfiguring them.
All in all its a 3/10 for difficulty.

Yes, it isn't difficult, just a bit awkward laying underneath the car manhandling the weight of it. You obviously got a decent one. I bought a DA1065 tool and found I still couldn't get it onto the nuts so use a 3/8" drive 14mm socket on a wobble end extension. Still not easy but gets the job done.