Not seen much promotion of the extra flights.
Its been all over the news media, to a national level (as part of the coverage around the Dawlish rail closure) and I even heard it mentioned in the House of Commons (during PMQ's I think), so I would say there has been quite a bit of coverage.
Bearing in mind that it'll probably be another month at least before Dawlish is re-opened, you have to think that BE will keep the extra flights going if it makes sense financially. It's a good
PR opportunity aswell.