OK, I got the car back from having new rear suspension bushes fitted & a new MOT. I've added the Tuner extension cable and joined the Blue flying lead to the White on the BMW loom and I can now receive AM fine. FM is also improved. Since your last reply I've taken another look at the installation instructions and it does mention that AM reception can be particularly affected where you have an antenna amp which doesn't have any power going to it. s'pose I shouldn't have been in such a hurry to get it fitted. Classic case of RTFM.

thanks again...

Marcus (beaker)
32 gig (various colours)