Cheers Dom and PigLick for your comments. I drove it to my local dealer (Milcars in Stanmore) and they completed the job this evening. However, they are keeping it in overnight to make sure it's well secured to the windscreen.
They couldn't say why the part had failed, without actually seeing the part (so if anyone happens to see it between junctions 28 & 30/31 of the M25 - clockwise direction - let me know....

). However, they were just as surprised as the people at Mini Emergency Service.
As far as I know, this will be covered under warranty, but I will ensure it is when I collect it tomorrow. Cheers again !
Paul