There are various maps available online including the very useful Old-maps uk website, which has terrific maps showing the UK as it was in the 19th century.
The maps on these pages were originally published in the Colliery Guardian in 1949, but they still give an good idea of where pits were geographically located. A lot of pits shown in these maps were active back in the 19th century, but you'll also see other collieries indicated which were inactive in the 1940s. Clicking on the numbered overlays will bring up more detailed maps, but be warned that due to the size of these maps the file size is quite large, so please be patient as the page loads!

These maps were kindly provided by Ian Winstanley, to whom I am much indebted for his support and assistance
Ian has list of collieries active in Scotland in 1945 which can be viewed at his Coal Mining History Resource Centre