FWIW, Because of the 20K interval (who does that anyway?), I'm betting that this- 'Castrol Edge Extended Performance' is the same as the JLR designer oil, and can be had at half the price, and is also available in both 0W-20 and 5W-20.
Our most advanced full synthetic motor oil providing an extended drain of 20,000 miles or a full year*. See how this oil is the natural choice for drivers.
www.castrol.com
And for the 0W-20 crowd there's also this- 'Liqui-Moly Special Tech LR'. Has JLR approval and states the spec right on the container (I've also seen a letter from JLR but can't find it). It's also half the price of the designer stuff at FCP Euro (may try this myself next time):
Special Tec LR 0W-20 by LIQUI MOLY
www.liqui-moly.com
I'm sure that the quality products mentioned from Motul, Pennzoil and Mobil-1 are just as good for those that change oil on a 'sane' interval.
(With my 3k mileage, I'm yearly)