Thanks for the info, my edibas is 6.4.7.
I checked my battery with INPA and it's set correctly.

I'm not too sure what to do now.
The battery is a Varta silver dynamic 12v 110ah 920a.
It was put into the car after 102790km (by the previous owner). Its now at about 131k km.
If I leave the car overnight the battery is at about 12.1v in the morning.
I gave a a charge (via the connections under the bonnet) and it went up to 12.5 and went into maintenance mode, so as charged as it would get.
I then checked this morning and it was back to 12.1v
Drove to work (35min) and when I got there I checked and i was back up to 12.5v, so to me alternator is good?
When I left this afternoon (car was in multistory all day) it was 12.3/4v.

This evening I wanted to check if any of my aftermarket kit was draining the battery.
My Dension 500s BT is switching off after 2min (LED on bypass switch goes off, can no longer see the BT connection)
The DVB-T Tuner is staying on after 2 minutes but switches off somewhere between 5-20min, I tested by leaving a mirror in the car so I could see the LED after I get out and lock the car.

So theres's no aftermarket kit that I have that could be draining it.

Do I just need a new battery???
If I do, is 30k km not a really short distance to kill it? (I know I don't know how long in time it's been there, previous owner may not have driven it much.