I’d also like to know what “demob” means

After WW2 the troops were demobilised - most of them - given a 'demob suit' for use in seeking employment in 'civvy street' and set adrift.

Chav seems to be catching on - it is much the same as Pikey used to be and is, I suppose, similar to what USn would call 'trailer trash'.

Any company gathering that includes a sandwich lunch is almost certain to feed you prawn and mayonnaise sandwiches.

As for retrosexuals, perhaps that refers to a mythical time when men were men and women were non-aspirational sex/mother-objects happy to find a bread winner even if he wasn't too clean and presentable. Almost certainly, a sexually successful retrosexual hasn't existed since the stone age and probably not even then! Actually, that makes even less sense than the rest of it - what on earth would a stone age retrosexual look like? Mumble, mumble...must go and shave.