I had the same issue on my car.
Tis an simple fix,
New instrument pannel from brakers / ebay max £30.
new speedo cable from local motor factors about £25
undo 5 dash bolts and remove top dash,
2 top bolt which hold pannel in place and pul towards you, (this snaps off the bottom 2 tabs which are a pain the ass to get to otherwise).
remove and replace.
follow steps backwards and all should be good.
speedo cable goes out of passanger footwell and into top of gearbox.
should take about 1 hour and save you ££££.
Kit
March 2009