Hello, I'm Keith and happy to help you with your question. It seems to me that a Statutory Demerger is quite a palaver and I wonder if it is worth the effort involved.
I lean towards starting an entirely new company for the additional trading just started. It will make life much simpler and you will get Entrepreneur's Relief to boot. The minimal activity so far can be passed through your existing business and the new company billed for the net costs involved.