What Kink can you sell on what platforms?
Just check out Sophie Ladder’s Amazing Spreadsheet of Platform Kink Rules
Sophie maintains this really useful resource.
On your own site you can sell anything legal.
UK Extreme Porn rules for Uk Creators
Read the Crown Prosecutions Guidelines and also be aware of laws about being unable to consent to actual bodily harm.
My cautious view (as this isn’t an area I play in personally) is that if you do the more severe end of CP, and ANYTHING related to blood, you probably need proper legal advice EVEN IF it is allowed on a platform. You are in the UK, that a platform allows content that is illegal here, isn’t a defense.