well, well, well, UK folks won't be any help. choice is either a dealer, or a good lock smith shop can cut you a new key. SIL lost a fob for his f150 dealer wanted lots of $$$$ and lock shop had the talent and stuff to make him a new fob, for about 1/2 of dealer prices. But he had to show...
if you need parts lots of salavage yards in the US just do a google
https://www.usedpart.us/database/junkyards/michigan/
https://www.roverlandparts.com/contact-us.aspx
https://www.uneedapart.com/used-land-rover-parts/
for hot weather operating (high temps ) works wonderful, old high mile engine, low oil pressure, oil leaks, etc associated with old engines works wonderful, come winter and it makes a diesel start harder, so needs to be changed to a lower weight oil