I've just had an e-mail from the BBC:
Thank you for your e-mail regarding 'Hotel on Sea'.
I am pleased to read of your interest in this programme. I understand you want to find out if the programme is a real documentary. It is a new genre called 'comi-doc' which is documentary with elements of comedy in it. The series contains real people and a real hotel: it is a documentary which was filmed over one year. Sometimes the directors accentuate the comedy element of the characters.
I hope this clarifies the matter for you and thank you again for contacting the BBC.
So it's a comi-doc. Much in the same way that Jeremy Blachman has a comi-blog. It's a wonder I ever manage to stop laughing.