OP – bear in mind that you wont be the first person to have had this treatment from this person, he will be very experienced in the ways of ripping people off, he will know what works and what doesnt. he will know full well what the legal process is, how it works and what you can and cannot do. he will play the system to his advantage. Lets say you win a legal case, that doesnt mean he will pay you. he gets x days (cant remember how many) to pay you, then he gets a CCJ against his record. The CCJ will stop him borrowing money amongst other things that may be an inconvenience to him, but chances are he already has several CCJ’s and they are not hurting him.
Your next step is to send bailiffs round (this costs you ) to recover the cash or goods to the value. He will have no goods to the value, he will ensure any stock is the property of a different legal entity. the bailiffs will return with nothing.
Your next step after this is to put a charge on any property he owns, and ultimately force him to sell it to pay you, chances are he doesnt have any property.
After that/inparallel you can force bankruptcy on him, again this is unlikely to bother him.
At this point you have won the moral battle, but you are still down £10k + legal fee’s.
You are an amateur compared to him. IN parallel with the legal route, get down there and start actually making life difficult.
I speak from experience of taking a ‘retailer’ to court and winning, and going through all the above.
Also – please name him so others considering a defender dont get similarly stung, or at least try and use this threat of public naming shaming to get some money back.