He was Chippy the crabman in this week's rewatch episode. I believe he appeared as Chippy/Chip and/or crabman in some other prior eps too. Not sure why he suddenly became Mr. Hubble. But that's OK.
Maybe his name is Chippy Hubble and he is a crabman
I think he is called Mr Hubble by Martin who would of course refer to I'm as "Mr Hubble". To everyone else in town he is known as Chippy or the crabman. That's my theory. Will be interested to see what he is called in S6E1?