Incidentally, there is a nice walk to be had along the coast path once you get out of Barry/Cadoxton back to Penarth, taking in Sully and the tidal Sully island (check the tide times) with a nice pub stop at Swanbridge. The only drawback is that there is a bit of a trudge from Cadoxton station to the coastpath taking in the delights of a main road and industrial works but it's quickly enough done.
A few weeks ago I picked up a book at the library, Edging the Estuary, by Peter Finch, in which the author walks along the coast of the (very broadly defined) Severn Estuary, including this section, and writes about history and people and geography and poetry and stuff.