No problem Jason, appreciate your time.
Fortunately I have also been doing some work on a 'mobile friendly' site recently and have been looking through my notes.
I now have some code which seems to fix the problem...
/* Disable iOS/WinMobile font size changes */
@media screen and (max-width: 600px),
screen and (max-device-width: 480px) {
html {
-ms-text-size-adjust: none;
-webkit-text-size-adjust: none;
}
}
yet to be fully tested, but looks promising so far
The biggest problem was the debugging, but Adobe Edge Inspect CC is a great little app