Hi Optimist,
It has taken a long time, but if your Freelander has a manual gearbox I think I have the answer. On mine it turned out to be the gear selector rods rattling. A simple check is to keep hold of the gear shift when pulling away with a little backward pressure. hey presto, the rattling stops. Same after changing to second at low speed.
I don't kinow if you can inject some light grease into the ball joints at the ends of the selector rods, this may help, otherwise it is just one of those things. Since mine has only done 30K, I don't think it cab be a wear problem
Cheers - Jonners