My 2005 TD4 had the engine management light coming on intermittently on the freeway, shortly after the fuel filter was changed at 100000kms/62000miles. (Prematurely according to the maintenance schedule). Code showed low fuel pressure requiring a new diesel pump. I suggest you have your car linked up to Land Rover Diagnostics ASAP.
My TD4 is also doing that - exact symptoms as above. It does it from about 5 miles into the journey, lasts for about 3, then it clears. It will do the very same thing the next day, at same point in the journey.
I also have a diesel leak (wet underguard under engine - not the leak off pipes as far as I can see). I'm hoping it is not the diesel pump, I believe these are expensive?
Suppose I will have to poke around underneath and source the leak, and get a diagnostic done.
This car has been nothing but bother since I bought it in Jan 09 - a real money pit....