The original post seems inaccurate throughout because although access to Bristol is undoubtedly poor (it was the vanity of the city council owners in the 1950s which caused them to turn their back on Filton, which would have been superb for access) but if there's one direction things are reasonably alright from it is Exeter - down the A38 and onto the M5 well into your journey. It's places like Bath that have a hard time getting there for the relatively short distance involved.