it is very easy to alter electronic mileage but trust me you would never get a clean adjustment modern cars store mileages in virtually all ecus whether engine abs or even airbags. in the original posters case the clock has probably been replaced but even a half hearted check would find the discrepancy, and yes its against the law for the trader to sell it with the lower mileage once pointed out without a major note on the advert telling people about the mileage.
i think early galaxys went through problems with the gauges going faulty under warranty and the new clocks were replaced but with zero on the clocks, also renault scenics etc . always had to have a note in the service book to the effect of the change.
as regards the imported vehicles yes very common , you would have the mileage corrected to the nearest figure because it would be in kilometres, being converted .
until the law is changed in the uk it is not illegal for someone to change the mileage on a vehicle it is illegal to sell the vehicle with a lower mileage without notifying prospective buyers.
i believe it is something to do with profiting from the mileage being changed.
i had a lengthy chat with a trading standards officer about this when i place a old nissan primera on a friends car sales pitch to sell ,he found a discrepancy with one of the cars and wanted them all checked accused me of clocking said primera....lol i told him it had 199thousand miles on the clock with full service history if i was so minded to clock it why would i leave it so high still took him 2 days to release it after checking (jobsworth).
again had a customer looking for a car spotted on a local forecourt he did a check and found mileage had been altered , told the garage they didnt seem bothered.
he reported it to trading standards and the car sprouted a mileage cannot be verified sticker.
not too sure if they can still use those now but used to be all the rage
