Jewels - even in the UK the only true way to identify what the car is is by the chassis number.
Generally the UK Reg plate does stay with the car for life , but it is possible to transfer the reg plates between cars if you want , or buy another reg number to assign to your car.
UK reg numbers do not expire. If a car has been off the road for a number of years it will still keep the same plate. There are a few exceptions to this , ie if the car was off the road from before 1973 when the DVLA computerised its records then the original reg number may have been lost , or if the car does not have a chassis number (ie vin tag been lost , car stolen and ground out etc ) then a Q plate reg will probably be issued.