Disco 3 (LR3) Strange Radio behavior

Recently purchased a Commercial Discovery 3 2006 and despite it having done 186,000 miles, it goes very well. The manual gearbox is taking some getting used to as I prefer auto, and it's not the slickest gear change I've ever come across but it does the job and I'm pleased with it.
My problem is with the radio, sometimes it will work and other times it's completely dead. Strangely the radio never comes on with the ignition and the button on the front has to be pressed to bring it on and turn it off, is this an LR3 trait as I've never known it before on any other vehicle, not that it's a major issue.
Usually however the power button will not bring the radio on and the only way to make it spring into life is to remove fuse 53 from the glovebox fuseboard, wait 10 mins and then put it back, the radio will work fine then for a couple of hours and then go inexplicably dead again. When the radio is working you can turn it on and off a thousand times and it's fine so don't think it's the on/off button.
Ideally I'd like to change the radio for a modern double DIN unit but it appears to be impossible. The Range Rover Sport which is based on the LR3 has many kits and options to replace the radio but they wont fit the LR3 despite the radio unit being identical. Does anyone know why this is, surely the Sport and LR3 have the same Canbus / MOST electrical system.
My radio is the Bob Basic CD400 unit and I don't have sat nav or any other goodies. Any help would be most appreciated.
Cheers Ian

Try a hard reset first, have you read the codes?

My D3 radio only comes on with the ignition if I have left it on when I switched the ign off.
It will also switch on and off with the button regardless if the ignition is on or off.

The high end D3 models (HSE/Metropolis) have all singing dancing Harmon Karden radios/set up.

These days I dont think mileage is the issue it once was as cars are no longer worn out with 100k on the clock.