And they might just be guessing mate. I would have the connections to the dash checked by an indie or look for yourself, and try resetting the ecu by removing the battery negative terminal for half an hour, remember the radio code, and when you put it back on, let the ignition sit on for 5 minutes - dont start it right away, when it goes quiet, no clicking etc then start it and see if the instruments work now. Take it for a brisk drive once its started, for a bout 10 minutes.
(The start up & drive procedure is not to do with your problem, just something you should do after resetting the ecu, so it can set the adaptive fuel trim again etc.)
It might not clear the fault, but a re-boot never hurts. The ECU is always running, even when the car is switched off, and can have a software glitch which could clear with a reset, worth a try. Its just a computer after all....would you never expect to reboot your pc? lol (if microsoft made ecu's.....they'd probably be the worst ecu's in the world...)
Could also be a bad or detached earth to the instrument cluster itself.