Bit of a result. Although my STB seemed totally dead yesterday showing 8888 on the display, when I got home last night, it was showing Err1. So I rebooted and it said it was doing a software update. It then sprung back to life. TV and broadband back in action.
I checked the diags screen and at 11.am it received some sort of update, then 11.07 decided it had a loader CRC failure. Reboot at 19:08 CM operational. etc. back in business.
So, just cancelled my engineer visit tomorrow and back to 4th april for the Samsung upgrade. With a bit of luck.