Ok here is the deal with ATF.
ZF 6HP requires Lifeguard 6 or OEM equilivant. It's base stock is Shell M-1375.5.
Lifeguard 6 is NOT a member of the ZF TE-ML 11B or 11A lubricant list. LG6 is slightly different which is why under the 6HP only see OEM equilivants listed and no reference to the 11B or 11A list of alternative fluids.
http://www01apps.zf.com/kst464/ZF_In...011_en0700.pdf
Regardless of what the bottle says Pentosin Product Data Sheet (PDS) states ATF1 is NOT recommended for the ZF 6HP. Pentosin ATF1 is a member of the 11B list (Lifeguard 5).
http://www.pentosin.de/flexxtrader/d...ATF%201_GB.pdf
Now when a bottle of ATF (Castrol Multi-vehicle for example) puts all these specifications on a bottle, what they're saying in best case scenerio is that that particular product meets ALL of those various requirements on the most basic level.
http://www.cartechbooks.com/vstore/s...=3578&CATID=21
Mercon SP and a Ford ATF ($4 quart) are also part of the Shell M-1375.4 family.
http://www.lubeandtune.com.au/html/lubekey.asp (Note: Amsoil sells an ATF fluid which meets Mercon SP, and when I asked about Lifeguard 6 for the ZF 6HP I was told that the Mercon SP spec is "on the low end" of the M-1375.4 family.
Now I've been told by Pentosin that there was an agreement between ZF and Shell over the Lifeguard 6 which is why ZF does not list an alternative fluid on their lubricant list, but their ATF1 would be fine for the 6HP when you're out of warranty.
As for cost? Lifeguard 6 is expensive becuase it's a lifetime fluid, so it wasn't meant to be changed. Your AT doesn't have a dipstick, and the refilling process is a PITA.
What would I do (In warranty)?: Your warranty is 50k miles or 100k miles max. If you're not getting the extended warranty just pay the dealer for an ATF change or find OEM equilivant fluid (Land Rover part# seems to be cheapest). It will only be a 1 time charge because you'll be out of warranty for the next change. Do the change before you hit 45k miles.
Out of warranty: Use whatever you want.
Note: Some people will say things like "well if you tune, you want to use X". Well here's the deal. My 335D puts out more TQ than just about any tuned 335i out there and Lifeguard 6 is the standard fill. And unless you're tracking the car all the time (unlikely with a A/T to begin with) you're probably fine.
From what I've been told if you wait until 50k miles to do a change, the new fluid will cause slippage because it does not have the worn off clutch material floating around.
Good luck!