Is it true that in the UK you can drive with a foreign tax disc for 6 months before you must get an English one? If so, how does this work? how do the authorities know how long a car has been in the country?
It is true - and we can drive in the EU on GB plates for six months.
Or six years as many ex-pats living in Spain seem to. :)
Police and traffic wardens fill in cards that specify the date, place and vehicle details of any foreign vehicles they see on the road and send them of to be recorded. Or they used to - I assume they still do, and now it would be so much easier with number plate recognition cameras - I'm sure they are set to photograph non-standard plates.