Both number plate lights not working...

[Advent]

My car Passat 56 reg 2.0Ltr Diesel 140 BHP Saloon car went for its first MOT today and failed which I expected.
I knew the number plate lights were'nt working and tried to sort the problem out myself, checked the bulbs they are OK, no voltage at the end of the cable with the light switched on. The drivers handbook does not have a separate fuse for the number plate light only the side lights and as the number plate is I presume on the same circuit. I take it then fuse is intact.
As the car is still in warranty untill next weekend I thought the franchaise were I bought the car from would sort the problem out for me today. Well they had a look a peep inside the boot but could not find the fault.
They advised me to take it to VW Pullman in Durham City before the warranty period expires. Now at the same time I do have an intermittent problem with the Near Side rear electric window VW know about this fault and as its intermittent I have to take the car in to them with the fault present. These faults are never there when you want them to be.
Could it be these two faults are linked somehow?
Any tips of where to look for the number plate light fault.
Thank you......