On top of not getting them to function properly, I decided to tighten them up just that little bit more.... and the alloy housing on the pod sheared

So I had to contact my brothers and am now beginning the no doubt lengthy and probably costly process of sending them back to the point of sale (I've dealt with them before and they are good) and waiting for Garmin to repair or replace.
On the positive side the alloy housing does appear to be quickly and easily replaceable (a wee bit like a gear hanger - which reminds me that a mate bust his gear hanger on his brand new Specialised carbon CX bike on Sunday on the second lap).
Needless to say I am even unhappier now