Of course I can have a personal account and a business account. There is nothing "naughty" about it.

I could even be selling the same type of product on both accounts, and that still wouldn't be naughty. One account would be selling items from my own personal collection, and the other would be selling items which had been bought by the limited company, with the intention of re-selling. However, I would never have the same actual item for sale on both accounts - that's where it starts to get dodgy.

It's a very common situation, with which HMRC are perfectly familiar. I have full documentation for all items owned by the limited company, and all my accounts and taxes are in order. HMRC has been made aware of the private selling account through my annual tax return, and my accountant is happy with my systems of keeping the two completely separate. 

Please stop trying to manufacture problems which don't exist. All these scenarios were dealt with in great depth when the possible issues came to light. No offence meant, but you are highly unlikely to come across something new, six months later.

You're not scaring me, but you might be worrying some less well-informed people unnecessarily.