Electrical gremlin

Strange one this.

came home late last night after a pint at my local. walked down the road to see my jag sitting there all lit up. headlights and tail lights. openened up the doors switched of the autoheadlights and started her up no probs ???? lights went off never to be seen again. as im off to hungary in her sunday i booked her into my local indie to read the fault codes and a general checkover.

All they found was the fuse for the obd had blown ??. and a whole host of fault codes for the glow plug system. the mechanic ensured me that this is always the case with the 2.7d engine even in discos and the xf. can anyone clarify or deny this please. not disbeliving my indie mechanic as they give me fantastic service. im just intriguied thats all. i wonder if the lights problem might be down to the recent heavy rains something like 12 continouis days of rain round these parts. but she would be in sleep mode after 40 minutes and had been stood a whole day.