At least back when I lived in the UK the Greenparty were the only national party which was Leftwing, though I believe nations other than England did had more mainstream left of center parties.

I was actually a member of the Greenparty until I left the UK following Brexit and at least the people in my local are were trully well intentioned people though quite naive (IMHO). Then again in the UK I worked for almost a decade in Finance - which was pretty much Sociopath-Central - so maybe it was me being significantly more cynical and skeptical than average rather than them being more naive.