www.jec.org.uk

I seemed to have stopped my speedo from working! I took the instrument cluster out to change some bulbs, in the process, I un plugged the mileage display, but just plugged it back in again. I put it all back together, but now when I start the ignition the car "bleeps" at me and I get a message saying "Er" on the heater display and the speedo doesn't work! I am not aware I have broken anything, I didn't drop it or anything and was very careful with it. All the other gauges work, the car starts drives, etc, everything is normal except the speedo doesn't work! I've checked all the plugs to make sure it is all plugged in fully, etc! I wonder is there something I need to do to reset it perhaps? I tried disconnecting the battery for a few mins, but it still not working. Any ideas?

Well if all the connections are correct, i.e. I dont know if its possible to connect any wrong way up, battery disconnect would be my first step

tried disconnecting the battery for a few mins, but it still not working

Never come across this problem, but this link to an old topic may be of some help:
viewtopic.php?t=2167

If a battery disconnect didnt help. I think you will need to remove again and make sure non of the contact/connections are wrong or damaged.

I think it is a loose wire in one of the plugs at the back, as I've been trying different things and had the speedo working twice, but when I the fitted the cluster back in the dash it stopped again, so probably a loose wire! How do I find out what ones are the speedo wires and fix loose wires?

Generally speaking when a wire becomes 'loose' after taking a plug off, its because the pin itself has come out of the connector.
They usually have a small 'barb' to keep them in th plug. You may need to lift that and push it back into the connector plug. (noddy drawing attached)

OK thanks I'll take a look at that and give it a try!