There are dozens of different kinds of pubs. The main purpose of a pub is to serve beer (to adults over 16), but most serve food to some extent - though that ranges from 'two pints of lager and a packet of crisps' via 'two curled sandwiches on the bar', through 'family' pubs (which is probably the sort you're thinking of - basic, usually microwaved, meals - though how 'fast' they are depends on how busy the bar staff are selling drinks), to 'gastro-pubs' - many of which are operated by Five-Star chefs and have to be booked in advance.

None of these would serve anything called "Mama's" or "Grandma's" though you might find the 'Publican's Special' at a family pub.

Actually, for the most part, the British define eating places by the cuisine rather than the building (I'm going out for a Chinese/Indian/Italian/Greek/chippie/kebab house...)