If someone was coming from the south of England then I'm sure you information would have been helpful, but assuming the OP is collecting his new car from near where he lives going into Wales via Bristol would not be a good idea.
Itguy mentioned that he wanted to explore some nice driving roads - so we just gave our suggestions, and I assumed that following the shortest route is not the main priority. We're also probably biased towards Bristol (but it really is a great place !)