Hi holding the P button down and pressing the power button for 5 seconds should reset the dish washer.It sounds like what your doing by holding down the P button on start up might be doing the same thing, as its going through a self test.This issue sounds like a blocked or partially blocked drainage pipe, I would suggest you first clean the fiter and manually remove the water with a small cup, then disconnect the hose and check if its filled with water.
If its filled with water check the train conenction to see if its the waste pipe or soil pipe.
If this doesnt work reconnect the waste pipe and look for a mushroom shape plunger about 3" in size inside the dishwasher, and try and gently lift it 1/2 inch up this is the overflow sensor the pump should start up and the water should drain.
If this doesnt work its most likly a fault pump, and will need replacing.Unfortunatly I can find your products manual anywhere so I can confirm what the 12 beeps mean but if you have the manual its most likly defined on the troubleshooting page. The newer variants such as BDW all have screens which display error codes, so assume the beeping is in place of the screen.
The system eventually reset, and I am guessing the overflow anti-flood switch reset. I ran a program with the system empty to flush and the system is working, but seems to be emitting a melting plastic smell. It does not feel excessively hot around the dishwasher, but I am worried there is perhaps a more fundamental issue with the washer.many advice? I don't want to run it if there is a risk of fire or further damage.