Thanks guys, I've gained enough confidence (and knowledge) to upgrade to 5.3.033, so have just done it and am quietly confident it will work.
I now seem to have another hiccup, it does not seem to recognise my additional tuner 'C' which is plugged into the USB port. It is only listing tuners A & B.
I've tried everything I can think of, including restarting GUI and re-booting but no sign of it. Any thoughts?