A primary resource for research into the historical is British History Online (see below). The Victoria County Histories are available on this site.
Websites
British History Online – British History Online was created by the Institute of Historical Research and the History of Parliament Trust. The website is a digital library containing some of the core printed primary and secondary sources for the medieval and modern history of the British Isles. Find it at: http://british-history.ac.uk/
A Vision of Britain Through Time – A website which provides statistics, maps, writings and more… Find it at: http://visionofbritain.org.uk
Old Maps Online – A website which allows you to search for historical maps. Find it at: https://www.oldmapsonline.org
National Library of Scotland Maps – Online access to the NLS maps collection, including old OS maps. Find it at: http://maps.nls.uk
Heritage Gateway – A powerful search engine for finding national and local records of historic sites and buildings in England. One can find historic photos, Listing descriptions and more. Find it at: http://www.heritagegateway.org.uk/
Historic England Archives – The archives of Historic England, including items in the National Monument Record. Find it at: http://archive.historicengland.org.uk
Ecclesiastical Buildings – Useful Resources
Lambeth Palace Archives Online Images – Incorporates the Incorporated Church Buildings Society (ICBS) collections (formerly available via Church Plans Online) Search for plans of churches online. Find it at: http://images.lambethpalacelibrary.org.uk
Corpus of Romanesque Sculpture in Britain and Ireland – A complete online record of Romanesque (i.e. Norman) sculpture in the British Isles. Find it at: http://www.crsbi.ac.uk
I have come across the following in my course of searching for resources, but have not really explored them to any extent. They may, however be of use to you, so I have included them.