Was it really a seaside special though, (ie an extra train in the timetable) or just a way of overcoming capacity issues which ought to be solved by the ongoing transfer of Turbos to Bristol area?
Maybe it was just a way of adding capacity, as it's certainly only adding to a route that runs year round, but I think running it earlier down and limited stops could have still been justified.
Edit: just received this reply from get:
"Hi, the weekend HST service will not run this year I'm afraid. Services are planned in line with passenger demand and route/stock availability and can be altered or removed in response to this. Phil."
Bit generic response , but covers it I guess.