This accent is an urban accent but is considered as typical of rural communities and so more traditional and old-fashioned. If an English person tries to imitate a farmer, a rural accent or that of a medieval peasant, for example, they are likely to sound something like the modern Bristol accent. Though of course a person from Bristol may not see it quite the same way!
It is rhotic, which means that the "r" is clearly pronounced in words like "card". In this respect, it is more like Irish and American accents than London accents. The "o" sound, as in "hot" also sounds more like the "uh" sound characteristic of American accents. There is probably a similarity with American accents because Bristol (and Plymouth) are big trading ports which historically would have been used for emigration to the USA.
Interestingly, the actor who played Darth Vader was from Bristol but his accent was not considered suitably menacing for the character!