Quote 1:
"Got a problem with the gauges on my Leon Cupra - when I first set off, the speedo doesn't read anything for the first couple of miles. The mileage reading doesn't increase either. Then it seems to start registering the higher speeds, and eventually wakes up to the lower ones too. Also, if the petrol tank is less than half full, the fuel gauge waves around between the correct reading and empty for the first mile or so"
Quote 2:
"Sorted. After a week and a half at Humphris, the speed sensor and temperature sender unit were replaced and it's OK so far. Seems odd that the petrol gauge would be affected, but I guess the wiring in these things can be pretty complex. A week and a half sounds a long time, but they had to order parts and they were generous with the courtesy car so I'm not complaining. And it came in at 325 quid which wasn't as bad as I feared to be honest"
Source:
http://www.seatcupra.net/forums/showthread.php?t=93171
I'll leave it to you to decide whether that's relevant or not!