Just reading through the thread again....... just wanted to make it clear that the notes I gave were for St. Patricks Causeway (Sarn Badrig) NOT Sarn y Bwch. I've not been down to Aberdyfi yet so cannot comment on crossing/rounding that one.
I would have thought though (as Jono says) that at high(ish) water there should be no problem.
Heres hoping the weather gets better than this!!!!