thanks for all of your replies, great advice.
Freddie is 15 months old, he's predominately lab with a few others thrown in, were not sure which?... most people comment that he might be a bit collie, german shepherd, or mastiv?

. no idea but whatever he is he's great!.
when we walk him up to the car boot he instantly ignores it, even if I hold a nice big treat out for him over the boot area he tries to walk away. when I lift him into the boot he sits down very quiet, once the car boot door is shut is pants and starts a very thick drooling. I once drove him to somerset. he was not sick for about an hour as there were no turns, as soon as we turned off at chippenham and the roundabouts start and he vomited all over the boot.
Luckily we have a vomited drill down to a T now, so there are lot of layers to soak it up for it get to the upholstery.
It seems to be to be a bit of both, nervousness of being in the car, and motion sickness.
I have heard that feeding him in the boot at the usual feeding times for about 3 weeks can cure car sickness, has anyone tried that approach?