[Nasher]

I've just measured 4 different sets of 6 bolt discs I have around the place.
All 8 discs come out at 9.5mm offset, on the unswept part not the worn parts.
With the 4.5mm spacers currently in place that gives 14mm offset either side.

My contact has confirmed the 748 discs are 15mm offset, measured the same way as I'm measuring the 9.5mm above.

That means of course that using the 15mm offset discs the discs will be 2mm further apart, or in other words 1mm further out, or offcentre to the radial calipers.
I've looked at the setup I've done on both my 1000ss and M1000, and both would easily accommodate this, but are slightly different.

Gaz, have a look to see if a mm either side would work for you and let me know.
I'm happy to buy the discs, which are available for a good price, and send them up to you.
You can pay me if they work, or send them back if they don't and I'll use them myself.