"But adding to the pressure on the long, lugubrious lunchtime drink is the threat to lunchtime itself..." Lugubrious means 'looking or sounding sad and dismal', and comes from the Latin lugere 'to mourn'. I'm not sure what the writer meant though - what's sad and dismal about having a drink at lunchtime? Sounds like a good idea to me
The expression HOBNOB has nothing to do with socialising around the hearth. Rather it is from Old English 'habbe' (to have) and nabbe (to have not'