Can indirect intention be applied to s.18, s. 20 of GBH and s. 47 ABH?
As far as I know, no it can't for any of them.
S.18 GBH/Wounding requires the defendent to intend to cause serious harm. (Requiring direct intention).
S.20 GBH/Wounding requires the dependent to intend to cause or recklessly cause some harm (Requiring direct intention or recklessness).
S.47 ABH uses the men rea of the underlying act. As far as i know, this can only be battery or assault so you would need direct intention or recklessness.