Right so two weeks ago my speedo was on about 53408, now its 64600, why is the speedo telling me I have done 9000 miles more than I have? although it's giving me an unbelievable mpg I'd rather it be accurate!

Sounds like the magnet inside isn't doing its job correctly?

The magnet just indicates the speed. The odometer is driven by gears and ratchet and pawl.

The speed that the odometer turns relative to the wheels is controlled by gears, a cable, and more gears. It's quite possible to see how it could under read if something was slipping, but over reading is very odd. Perhaps if a cog's worn it could be rubbing on the one next door, and bypassing one of the reductions? Whatever, you'll need to take it out for a look, and then replace it if you can't see anything.

Either that, or you need to stop leaving the keys in it.

Ah of course I forgot about the gears only had one apart a month or so ago

what dictates when it turns is there a latch I could have knocked out of position when re paining it ?

There are small clips on the digits. Take it apart it's quite interesting..
Don't take the needle or face off though