Cheers Sausage. I'm wondering if it has a dead cell. The starter seems good as it's cranking. The fuel pump has been struggling for some time now (the whine on second click of key lasts nearly 10 seconds and at over 50mph its really working hard to pump). I've got some easy start that I sprayed in last night but the battery was too dead to even consider cranking (I'd already tried cranking before the easystart).
I figure the battery has a dead cell from listening several times and it only holds 12.2volts fully charged. Now I know it can hold 12.5volts and not crank because ultimately ampage is what allows the motor to fire. I've gave the starter several taps and I have a replacement but the starter is engaging so I don't want to carry on removing it.
Regarding Fault codes I put my OBD reader on it the other night:
16502 - Coolant temp sensor failure (which may explain the rough starting previously).
17972 - Throttle body alignent - poor batter voltage (this may have been on the ECU some time).
17566 - MAP sensor - never had a bad start condition due to MAP?
16786 - EGR valve faulty - again common on VW and this has been sticking for a while.
16555 - Bank 1 too lean - this leads me onto the fuel pump issue although I'd imagine it'd be an issue at bank 1, 2, 3 + 4 not just one? Also could be related to Mass air flow sensor too.
I've got a new battery to try tonight and a new fuel filter incase the fuel is struggling to get through an old clogged filter (not sure on the last change).