This is an excellent private website run by Peter Higginbotham- which is continually being updated. Not only does it give much general information, with illustrations, of how the workhouses were operated but also includes useful information on individual workhouses.
Map showing Bishop's Stortford Workhouse circa 1897
Up to August 2001 it had pages for the Barnet, Bishop's Stortford, Buntingford, St Albans, Ware, Watford and Welwyn, including maps (such as the above example), photos, lists of staff and inmates in the 1881census and references to surviving records. There is also some basic information on the other workhouses in Hertfordshire.
See also Hertfordshire Poor Law Unions
If you can add to the information given above tell me.