I have the same problem with my TD6 2003.
On medium cold mornings, I can release the handbrake, put it in D and nothing happens, I can even rev the throttle a bit, and then after a while it will gently start to move forward.
however if I put it in R it creeps backwards as normal, also if I manually select 1st gear it crawls away fine.
on warm, or very cold days it works fine. My mechanic friend has suggested it may need a software update on the gearbox. He suspects the Torque converter is a bit lazy on cold mornings around 0-5Deg. C.
My Son has a USA SPEC 2003 HSE 4.4 Petrol, and his doesn't do it, but there again his RR has a different gearbox.
Anyone else experience this, and have a solution?
Do u think that gear is engaged and brake is holding you?
Mine feels like it is not engaged till i step a little gas.
Something i experience last days is in moderate accelarition while upshifts from 4 to 5 it first lowers the revs,hesitates then shifts up.