Thanks for your responses,
I spoke to Harrison pointing out the issues with the trim that they supplied. They told me that they have sold these to other DNA builders and they have been fitted without any issues. I haven't broached the issue of returning them yet because I'd like to hear from anyone that has sucessfully mounted a set (or bought a set and given up...).
On the plus side I've contacted my local BMW dealer and they can get me a set of the official BMW bits for around £110, all in which isn't bad.
So, I'm still hunting for anyone that has sucesfully used the Harrington bits???