There is a pixel fix available on ebay and places, but all it shows you is how to strip the clocks and spray some contact cleaner where the ribbon joins the circuit board (I've tried this with a variety of results none that good) so don't bother spending money on this. Look in autotrader or online autotrader.co.uk there are some firms that repair the clocks but charge up to £200 personally I wouldn't be too worried most people know this is a really common fault. Milage can be verified at the dealer and through Hpi anyway. It is annoying though!!
On a different note if your in the Greater Manchester area of the UK having trouble with your BMW I found
http://www.bmwrepairsleigh.co.uk to be really helpful and new there stuff. (I'm not from that area but happened to break down nearby)