Weird starting fault - mk2 Octy

Hi there

My Dad has a 56 plate Octy 1.9 105 taxi. A generally very reliable car and I am about to get one myself!

However, on Monday, after filling up the car conked out and would not restart. Putting a diag reader across it showed MANY faults all seemingly unrelated. The only one he can recall is fuel level sender? The guy running the diag at the time believed all the faults were related to the canbus. I'm not sure what this means but my googling skills reveal that the taxi meter is possibly spliced into the canbus and it was very recently recalibrated (prices went up). Is it possible this is somehow causing the non-start fault?

The car is currently with Skoda who don't seem to know what's wrong and are about to charge him for changing the loom and possibly ECU... over 2k!

Any pointers very much appreciated.