Oh dear Supa, I am affraid this is not good, not good at all.
DO NOT RUN THE CAR !!!!!!!
I know I lark about a bit on here but please take this seriously.
You should NEVER run a HDi with ANY petrol in the mix.
The High Press pump relies totally on the Diesel for lubrication, the petrol will clean away the oily Diesel and this will result in the metal components of the pump effectively rubbing together and wearing prematurely.
This will effect the pressure the pump developes and will lower the overall performance as the injector spray pattern will be effected.
The car is still likely to run after this episode but the pump will have suffered an assault.
The louder noise you can hear is the Petrol mix effectively 'exploding' in the cylinders as it meats the highly compressed hot air, this is also detrimental to a Diesel unit as Diesel does not explode in the cylinders like petrol does.
Tis a sad day........
Me, personally I would drain the whole tank, change the fuel filter and replenish tank with Diesel and a bottle of fuel conditioner (Forte) and see how it goes, you can get a Fuel pressure reading off the ECU during a code read and this may well show a drop in normal operating pressure giving you a choice of what to do.
Some, would get rid quick
