I'll keep that in mind. Building a branch from scratch seems like a very hard task especially in a very conservative area. However I do want to get into contact with other socialists and maybe do some political work in an organization. So it's either ISO or start a branch with Socialist Alternative or Socialist Action (who has also asked me).
Yeah, the CWI, in my experience, has been relatively far more tolerant. Of course there are limits, often more in a practical sense as there is little room for longrunning debate. Papers are written with a 'broad mass' in mind that should be convinced of joining the CWI and strike. 'Discussions' have more the character of rallies and dissenting views are tolerated, but not encouraged in any way.
That is better than most other organisations I guess. But if you're going to start from scratch on a local level anyway, there is little point in joining I think.