These tyres are not available anywhere, period.
I've spoken to BMW UK, and they have said the only options open to me are (and they accept this is BMWs problem and not mine)
1. The dealer provides a replacement car until such time as a tyre is available
2. The dealer provides you with a different tyre and I pay for the 2nd tyre to keep the axle the same.
Those are the only options.
BMW seem to offer the Dunlops as the only other tyre...
Spoken to local garage, they are going to repair the puncture for now so at least I have something, I don't want to be given some crap 116 as a replacement for an unknown period.