What's a patronal fair? What is Whit Monday? The Brown Cow Inn??? Sounds udderly charming! And what on earth is a treen??

Patronal fairs were (are) celebrations held in honour of the patron saint of the village church.
Whit Monday is the day after Whitsun, which is the seventh Sunday after Easter, when the day of Pentecost is celebrated in the Christian church. It is derived from White Sunday, a reference to the white baptismal robes. Whit Monday has been a day of festivity for many hundreds of years in England, until it was replaced about twenty years ago by "Spring Bank Holiday," on the last Monday in May.
"The Brown Cow" and similar names are fairly usual for pubs in this country. Not far from me (about thirty miles away, over in Yorkshire) is a pub called "The Craven Heifer," which seems to signify a pusillanimous young bovine female. In fact, Craven is the name of the district in which the pub is situated. My own local is named "The Green Dragon" and, in the next village, there is a pub called "The Bay Horse." There is also a Yorkshire brewery known as "The Black Sheep Brewery" - and very fine ale it produces, too, (although it goes against the grain for anyone in Lancashire to say anything good about anything Yorkshire !)