Bought a new keyboard and mouse combo for the new telly and eagerly connected them via a simple USB dongle. It took a while to realise why neither item worked until I checked the box and it proudly confirmed "Windows 10" ready.
The TV is based on Android technology. D'oh.
Yet not all was lost as I tried the keyboard and mouse set from our Minix box (the Windows based one) and all worked fine with the TV. I then connected the new set to the Minix box and that also managed without a hitch so all is well at the end bar a few skipped heartbeats.
We are now really wired up for the 21st century on both TVs and hope that's the end to it.