The best maps covering the British Isles are those that are produced by the Ordnance Survey. However, you should beware of a few pitfalls that need to be considered.
The original surveys started in 1784 and updates, such as railways, were overlaid on later maps. Thus, a map may show a village as it was in 1790 with a railway built in 1850 running past it. A second survey started in 1840, with subsequent editions updated in the 20th century. These produced much less anachronistic impressions of places as they really were at the time.