Ok time for an update, sorry it's been so long coming, but I've been working away for a few days.
Anywho, the car is running fine now and it turned out to be the brakes after all.
I don't know how I missed it because I'd had the shoe assemblies off, albeit all in one unit, I'd tried to drive it with the handbrake cables off and had no joy, however, when my dad came round to help fit the new diff, we got as far as popping the drive shafts out and while I was underneath guiding the splines to a safe area my dad tried turning the drum, it didn't turn.
We took the drum off because at this point it was obvious I'd got it wrong, and while we were doing a piece by piece analysis of the shoe assemblies my dad noticed the cam on the bottom shoe which the handbrake cable connects to was stuck in a weird position.
Turns out it had popped out of its hole and got itself wedged in the opening of the shoe so it was stuck in the handbrake 'on' position. A swift tap with a hammer from dad and it popped back in, we tested the cable for any seizure and the shoes for free movement and the cylinders for full range of motion and they were all fine.
We put everything back together and it drove.
Consequently the prop is back on and the car is running exactly as it should, some axle deep mud yesterday proved that.
I don't know how I missed it, but having a different (more experienced) pair of eyes and some daylight helped.
What we did notice is that when the handbrake cable was off, even pressing the brakes would cause them to jam on, we think it's because the whole shoe assembly would move because of this one stuck little arm.
When I say stuck, I mean stuck too, this thing didn't even release when I had the shoes off on the floor. Also, because I was working on a hill and in the dark every time I was working on it, I had to press the brakes, there was no way of getting the car out of gear to start it up without it rolling off and there was too much traffic and too close to neighbours cars to start it rolling then crack the engine etc.
The two things I can't understand is why at one point both back wheels were locked and why it did this in the first place while the car was on the move.
I opened up the o/s drum to check all was happy there and for reference and that's all fine.
So yeah, I now have a really nice diff sat in my shed. If anyone knows anyone who's after one then point them at me as I'd really like my £80 back!
I know I maybe stupid enough to make this mistake, but I'm not stupid enough to not admit when I'm wrong. I'm just glad my dad spotted it when he did as it's saved me the cost of a vcu too.
Oh and I was looking though the RAVE manual and noticed all the pdfs were daft names so I named them all properly and got rid of the cheap interface so now I just have the RAVE manual extracted as pdfs by vehicle that you can put on your phone without the installer etc. (providing your phone lets you view pdfs)
I tried to put it them in a post on the forum, but they're still a little too big to upload. Let me know if you want 'em
The things you do when your car is busted eh...
Anyway, thanks for the help folks. This was a confusing one!
Peace out
