The National Archives UK website has recently added a searchable index of records of 23 Poor Law Unions in England and Wales. Images of the original records can be downloaded free. The records start in 1834 and extend to 1871 in some cases.
The records don't just include the names of the poor, for example, the Truro Poor Law Union has a "Statement of Medical Officers' and Schoolmaster's and Schoolmistresses's Salaries" for the Quarter ended Christmas 1848.
I've already found a petition from several residents of St Agnes in Cornwall (including one of my Boundy family members) requesting that the parish should not be moved to the Camborne Union.
I'm sure there is lots more to be found.