E60 530D Main fan running at high rpm

04 530D 95k miles (No other issues)

I started my car today engine started no problem, 2 seconds later the fan kicked in at high RPMs! It's so loud it drowns out the sound of the engine even with the bonnet open!.

I left the car idle for about 5 minutes to see if the fan would stop but no luck, checked all the fluids etc & the engine and oil temps were normal so I went for a 10 minute drive. Cool wet day around 10c/50f

The car ran normally without any warning icons on the dash/iDrive.
Got back home turned off the engine let it cool for a bit started the engine again and of course the fan kicked in running at a crazy speed, the damn thing sounds like a huge vacuum
First thing that came to mind was the thermostat is fried so I decided to check around the net to see what I could find and yep it sounds like either the temp sensor or something linked to the thermostat.

That was all fine and dandy until I started the car again same issue with the fan running constant and at high speed but then I turned off the engine and heard this weird (what I can only describe as) an electronic beeping or an alarm that had been hit with a hammer this beeping stopped after about 30 seconds but beeped twice when I unlocked the car with the remote!

So is it the thermo making the fan kick in at a constant high RPM?
And what the hell is that electronic beeping sound?

Anyone help a fellow bimmer nut out before I get hijacked by a main dealer ?