In Part two of my update, I mentioned I had modded the fist mic, well, with more reports of it being a little quiet we swapped the capacitor/resisitor that we fitted with another single capacitor from the kit. This gave even more gain and worked a treat, i now run the rig with 60% audio gain and Comp 1. This improves the FM response, we also found the mic element was not seated correctly.
Thanks to Derek G3WHK for his help in modding the mic.