As Ranger says there was a route to Gatwick from BRS.
It ran from 1999 for about three years and was operated by Brymon/BA via PLH in both directions.
DH-8-300 equipment was used but the timings were somewhat bizarre as far as Bristol was concerned. The flight left BRS in early afternoon and returned mid evening.
I don't know how many pax used the service from BRS to LGW (it was flight number BA 4008/4009) which I believe was primarily intended to be part of the several daily PLH-LGW services and, presumably, used the BRS aircraft because it was available.
Going back forty or fifty years many (many in those days would not be many to our eyes today of course) of the Cambrian and Dan Air scheduled services operated BRS-CWL or CWL-BRS to a destination such as Paris, and even Liverpool. This lasted for many years, although I'm not sure if it was possible to book BRS-CWL (or vice versa) legs on these journeys.
Indeed, until the advent of Air Wales which ignored BRS completely (I wondered at the time if this was a mistake), Welsh-based airlines such as Cambrian, Airways International Cymru and InterEuropean Airways, used BRS and CWL as almost twin airports for their operations, although that is not to say it was possible to use them to travel across the Severn (the last two were charter airlines anyway).
Talk regularly surfaces in the local press about a hovercraft connection between Bristol or Weston and Cardiff, and it must be remembered that in the 1930s the air service betwen Weston and Cardiff was one of the busiest in the world at certain times of the year. But there was no Severn Bridge then of course.
Finally, the government has announced a major study into the feasibility of a Severn Barrage. Could this yet mean one airport for South Wales/West of England in the estuary:
