Most members believe the Green vision is not compatible with capitalism, although some departed leading members, including Porritt, choose to believe it is. The Party is itself a coalition between its environmentalist and electoralist right wing and a left which is libertarian and anarchistic. The former is comfortable with the traditional party form and conventional political activity. The latter could have rejected the idea of party altogether but has instead tried to reinvent it. As a result, the Party's national committees have almost no power to instruct the local parties to do anything.
Candidate selection is entirely a local matter.
Decisions are usually made by whichever activists turn up to a meeting to make them. The Party Conference supposedly consists of representatives of local parties, but in practice almost any member who attends is allowed to vote. But political parties traditionally do not enter into alliances. They compete, not cooperate. Greens want a party, since that maximizes their opportunity to engage with national political debate.