OP, I'm a solicitor. I read your original thread and have seen the TA review.
The owner of this place is seriously deluded. Tbh I thought even on their own website it looks like it's seen better days and I wouldn't have wanted to stay there, but clearly some people do as he's managed to garner some recent positive reviews (assuming they are genuine).
He always berates anyone who leaves a poor review, blaming them for not addressing issues during their stay or (one of the latest ones) accusing them of leaving without paying. I think you actually have him on the ropes here, hence why instead of calling you a liar in his TA response he's got some legal nitwit to write a letter for him.
I would advise you to check out the law firm/ solicitor online, either the company website or if they don't have one, on the law society page.
I would ignore it. If it goes to court you can represent yourself, but there's no chance it'll go that far. He is as full of hot air as an overly inflated balloon.