once you had disco 4 you will not want anything else,
get as late as possible as common faults mostly resolved,
if not getting commercial be careful which year you pick as some early 4;s are higher tax.
some have spun shells but i think its quite rare, there is a specialist engine re builder on the discovery forum he took a tally over 12 months and it really was no where near what i expected and put into perspective how in-frequent it was.
I think this was made into a big issue as LR were poor at first on sorting it and secondly the cost they were charging for a new 3.0 engine!
i were looking on a selling website and it seems to suggest that 2014 models onwards are £330 a year road tax, and pre 2014 are about £500. Is that correct?