The Cube Reading Minster - played at Downshire Square (don't know exactly where that means as I can't see how to fit a football pitch into that area), then at Caversham Place Park (i.e. what is now the BBC Monitoring Service place) and then at the Rifle Range at Coley (that's the first field south of Coley).
South Reading - played at Whitley Park Farm and then later at Mr Colebrook's farm - at least one of those is the Cintra Park area.
Cube - Do you know what became of these two clubs?