Hatfield
There are 2 bars in Hatfield, The Ele House which is open every night, till 12 on Saturday and 10.30 on Sunday. The Font Bar (previously the hub) is the main night club venue. This is open every night for quiz's, comedy nights, drinks promotions and other events such as alternative music, on a Wednesday and Friday there's a late licence and it's open till 1am. The Font Bar was extensively refurbished summer 2002. £500,000 was spent apparently.
St. Albans
This is a city campus site and chocka with law students, so although there are no bars, I think you'll probably find plenty to amuse yourself. St. Albans town centre has bars like Vintry, the Bell, and a new bar called Casa. Many students prefer St Albans to Hatfield.
Information on events can be found on the university's students' union website. There's also info about the changes that have occurred as Watford and Hertford campuses were closed at the end of the 2002/2003 academic year.