We are currently in the process of renewing our public liability insurance policy, you might want to also checkout Westminster Indemnity Limited as they offer reasonable monthly payments, especially if you’re a non profit group (put income as £1 in quote as £0 doesn’t work). They also don’t specify the number of members of in your paranormal group which is an advantage over Blackfriars Group, especially if your group is quite large or might want to expand. There’s nothing stopping you from getting a quote from both.

If you’re a paranormal group that offers public investigations or events, you might want to check out Event Insurance Services. I haven’t dealt with them directly, but I understand many paranormal groups use them.