Turns out that there isn't an issue with the searching of assembles, it just comes down to a really poor pickup reception with the X5 e70.
There is no option to search for an assemble, they just appear or vanish.

As I drove around yesterday, I left the DAB assemble selection on screen, to which ...

I've recently acquired a MY2010 E70 40d, and although it's a lovely drive, there are a few things that need to be corrected.
One issue that I've found is that although the DAB works, and there are a number of channels to choose from, i am unable to search for more.

From the CIC menu, i select ...