I agree the first thing I do is look at the rear boot where there is likely some sort of rust, damage or the sils and gauge the age, but the electronic clocks its the easiest thing to do due to the Eprom codes and Ecu's used as its not a safety item the chips are cheap as chips
Look a price list if you want clocks to any millage you want!
Volkswagen
Model Year Price
Bora All £90
Corrado All £90
Golf 3 All £70
Golf 4 -2000 £70
Golf 4 2001-2002 £90
Golf 5 2001-2004 £120
Golf 5+ All POA
Lupo All £80
New Beetle All £90
Passat -2001 £70
Passat 2001-2002 £70
Passat 2003+ £120
Phaeton All £110
Polo -2002 £70
Polo 2002+ £80
Sharran -2000 £70
Sharran 2001+ £90
T4 Transporter All £90
T5 Transporter All £90
Touareg All £100
Touran All £120
General rule is average is 10,000 miles so after the first MOT it should read 35,000 to 45,000 if constant with service logs! If on the third year it had been sitting on a forecourt then millage might be closer to 35,000. If it was private then might be closer to 45,000 miles, but you just don't know unless you see all the documents after the first MOT.
The footwell is always a good start the rubber pedals and worn carpet area which you rest your feet. The way I see it your not gonna buy a car without most of the MOT's in place.