Strange Clio fault

[Fake Concern]

This afternoon we all went out in my daughters 1999 1.2 Clio. Stopped for a few minutes, then start car to go home & the tacho went mad, showing no revs then 7000rpm all over the place, but car driving normally. When we got to a junction, I suggested she turn the car off & re start it to see if it clears it. She turns engine off, then the car wont re start, (I was popular as you can imagine!) but the rev counter shows 7000rpm with ignition on (engine stopped). We called the recovery truck & the driver plugs in his code reader, which then says it cannot connect with vehicle on 2 or 3 tries. Next time it connects, doesn't show any fault codes, but now the car starts and the tacho back to normal! We drove home no problems. The recovery man suggested it could be the throttle sensor, but no warning lights were on and no code could be read. I suppose we will have to leave it & see if it happens again, but anyone have any ideas?