Peugeot 307 no ignition, flashing dash lights and beeping

Recently a fault popped up saying (Braking system faulty) thought it was the ABS?. Car still drove normally. All of sudden, whilst driving, the car switched off everything, lights and engine. When I tried to turn the ignition, a whole bunch of lights started flickering and beeping noises went crazy plus wipers started moving without any buttons or switches used. There was also clicking noises under the bonnet by the fuse box which I think were the relays?

New faults popped up saying economy mode and anti pollution fault.

I tried the whole reset BSI thing which made the car act normal for a minute but moment I tried the ignition, it went back to its crazy flashing and beeping state.

I used a multi meter to test the Voltage on the battery terminals which read 12.5/12.8V? Is that enough?

I checked all the fuses inside the car and under the bonnet plus the maxis under the fuse box. All were fine and not blown. However, I did see a little oil residue inside one of the ports of one or 2 of the maxi fuse inlets?could that be shorting the electrics?

If it was the battery, surely it wouldn't be flashing and flickering. And surely it would just act dead in general and now allow me put lights on and open windows or even get some sort of life from the dash?

Fuse box concerns me with the slight oil residue which could be causing a short? But if its not that, what about the alternator?

Or maybe the BSI unit is fried?

Any suggestions would be greatly appreciated. Thanks.