I don't know of one - have you tried the RHS website?

Mostly that depends on what purpose you are planting them for. If hedging, the rule of thumb is spaced at 1/2 the desired height of the hedge. Prostrate shrubs for groundcover: far enough to touch after 2 years growth, when in staggered rows. Planting farther apart means waiting longer until it fulfills its purpose. Planting closer together may mean removing deaders after a few years.