With high speed rail available from Belgium / Northern France to London, I really can't see OST to anywhere south and east of London working.
However OST to EDI or GLA might be a goer, surface transport being a non starter unless you're particularly into trains or buses! The market is always likely to be more inbound tourism, as the bucket and spade traffic to the (excellent) beaches on the Belgian cost, between Koksijde and Oostende are sadly a thing of the past - UK travelers preferring the more "British" destinations of Benidorm, Mallorca and Turkey! And of course the weather isn't that much better than Brighton or Margate.