It's okay - I've rhymed "Portacabin" with "or to Gavin", and it seems to work. (I don't particularly like Gavin, by the way).
I agree that Charles Bronson rhymes with Mr Johnson, but it isn't paticularly romantic sounding. Seeing as Oban is a port with boats and a harbour, I might rhyme it with "coxswain", especially as it's a bit of a suggestive word. I think you can be suggestive while keeping a romantic quality.