Hi Cliff
As far as I am aware the most Easterly point that dolphins have been seen up the Welsh side of the Bristol Channel were a group of Rissos off Kenfig River a year or two ago.
I have now been informed of a pod of dolphin (believed to be commons) off West Nash Buoy which is 3 miles SW of Porthcawl Breakwater. There is video footage available which should confirm the species and I am trying to obtain a copy
Thanks for this Steve would be great to see the video!