I'll give it an 8 -- much better than ep 3, even if it was scripted. (I suspect my score would have been lower if I hadn't seen episode 3.
What saved the motor caravan segment, for me, was the staging. Putting Hammond's "van fire" and the Citroen's rollover in the background was very reminiscent of Blake Edwards' Pink Panther films, where the primary actors (but not the audience) were unaware of the action going on. A classic trick, when done well, and it was done well here.
SIARPC, well, it's on a par with Tom Jones, right?
Road test? I liked it, really; pretty girl was a good idea, mainly because they don't use it very often. Really should have stuck with the vuvuzela music, though.
I will note that no commentary was made whatsoever about the infamous YouTube video. Pity, that; I'm sure it could've added something. I also note that no one took a turn round the track in the Robin, which is also a pity.
Incidentally, a question: is there no such thing, in Britain, as pickup campers?