I have studied the subject and the maps, and I've come to the conclusion that Seafield Terrace must be the row of six houses with arched doorways. Between the end of the row of six, and where the original end of Wensleydale Terrace was (which still has a blue enamel sign on it) and the Tile Sheds Office 'new' houses have been built. The current gap between the two terraces is where the end of the tile sheds railway line branch got close to the road. I think there must have been a loading area between road and rail transport at that point.
Now I have said all that, the current row of six houses stands on the site of a previous row of six houses, the original six facing inwards towards the tile sheds and with beautifully arched front doorways. The 'new' terrace faces outwards toward the sea, and the arched doorways were replicated.
This is a drawing of the old tile works showing the old row of six terraced houses on the right.
The image predates Wensleydale Terrace, and you can clearly see the stand alone building that must have been the Offices by the road. Blagdon Terrace can also be seen in the background by the railway bridge.
I hope you find this information to be useful. Sorry that I cannot state with 100% certainty that the row really is Seafield Terrace, but I think with the evidence we have it must be it.
P
