Hobgoblin should be served at 'cellar temperature', which the licensed trade (and CAMRA) recognises as being roughly 12C to 14C.
Storing it in a fridge won't harm it (since it's not 'bottle-conditioned') but it needs to be taken out of the fridge well in advance of drinking it, so that it can reach the correct temperature. (The same applies to white wine. I want to howl in anguish when I see people serving white wine straight from a domestic refrigerator!).
Alternatively, Hobgoblin can simply be stored in a cool place but, if necessary (i.e. on the rare days when it actually gets hot in this country), be given a short spell in a fridge before drinking it.