PitchFinder is an easy-to-use searchable portal of football facilities across the country and is completely free to use.
You simply have to enter a postcode, select your desired radius - say 5 miles - then click enter. All of the football facilities in that location will then be plotted on an interactive map.
You can click to expand each site into a separate window, which will give you key information about that site. This will include the type and number of football pitches, or whether there is changing or parking provision.