After 3 years of solid BT connectivity, Bluetooth just disappeared from my machine this afternoon. 

No option to switch it on or off, all devices still showing as paired but "Bluetooth switched off".

Tried a few suggestions from various forums but ended up re-flashing the BIOS with the latest (which was already installed) and now its back to normal & working ok.

Thought I'd make a note here in case it helps anyone... and so I can find the resolution easily if (when?) it happens again.