The digital project Hansard 1803-2005 offers free access to digitized volumes of the Hansard, the official parliamentary reports of the United Kingdom. The Hansard contains only transcripts of parliamentary debates. The website provides lists of bills and acts.
For finding additional information you can start by looking at History of Parliament Online, the History of Parliament, the section Living Heritage of the Parliament’s website, and the web pages of the Parliamentary Archives. The website of the Parliament has now a section about the First World War.