I know on the old forum there was a thread about this and I never got round to reading it all. So which was the best option for third party insurance.
CTC
Everyday Riding
BCF

If you don’t mind saying again any experience of any of them.

Check your house contents insurance as you might have third party liability cover under that. The company I work for provides it for “private pursuits” which covers biking though I don’t know how the covers compares against the three you mention.