*Update*
I've spoken to a MB main dealer and they wont give me the part number.
They quoted £458.40 for the loom.
I'm hovering whether to go for that as it's a genuine MB part and whilst I could make one it would take quite a bit of time and no matter how good it still wouldn't be genuine MB.
I'd still love to know the part number or where I could go to find this out as at least then I could look for a 2nd hand loom.