Hello all - what can I say! I am sorry about the spam and thank you to those of you who have persevered and posted throughout.
I have now blocked all of the random users and I'm in the process of deleting all of the random spam messages. I am sorry if anyone gets a post deleted or accidentally blocked as part of this process.
I have added additional security to prevent this happening again - I am keeping the security settings as low as possible as it means extra steps each time you post, but I'll monitor and keep tweaking it up if the spam continues. I'm on it now!!