Can anyone explain this please?

[ModifiedMadness]

personal mileage (the one under the full mileage - is there a proper name for it?)

It's called the Tripometer mate, the other is your Odometer

[gazza1286]

I would think that you have a loose connection at the battery.

You need to check that straight away. If the battery disconnects at speed you'll loose the lot- - -

Lights, brake servo, power steering

[ModifiedMadness]

You're not the only one mate don't worry, I'm the same

[phat6n16v]

if it was when you started its probly your battery is goin flat mine does it when it feels like it as in the cold.
nought to worry about.

[danny_boy]

a similar thing happenes to my car

[Robdeforma]

Yeah the same thing happend to my car, about 2 days after I got it i was holding it on the clutch on a hill and all the gauges and power went mental. The gauges started going up and down really quick and everything reset itself. It only did it for about 10 seconds and then went back to normal but with everything set to 0. Didn't think much of it coz it had gone back to normal. Never happend since!