Hey there, got a 2.3l petrol, but i'm pretty sure the dash should be identical! my dash was doing the same trick, so, unclip the dash pod from the back, and it hinges forwards, and should gently pull clean off, (clips straight back on again!) and then there are four screws, round the edge, one virtually in each corner. these 4 hold the dials to the main dash. once these have been removed, the dials unit will come off. after having pulled this up, you'll see that there's a main connector, going to the back on the unit, disconnect this, give it a light wire wool-ing, get the shine back into the terminals on the unit side. give it a good blow to remove and wire wool left, and prevent shorting between contacts. right. now, take a small strip of card, (playing card thickness) and cut it into a rectangle to fit behind the contacts. (the contacts are on the unit side, and they're a peice of flexible plastic wrapped over a shaped piece of plastic). once the card's pushed behind, it'll make sure there's good contact between the terminals, and the socket. give the socket a good blow out, make sure there's no **** in there, re-connect, and assemble the dashboard. hopefully you should not find that it all works well, and all the little lights on the dash will glow brightly, just like new!

hope this helps,
cheers, ben!