I bit the bullet this morning and dumped my fickle client. I have no regrets. The email I sent yesterday that went unanswered was answered this morning - it was a public holiday in my client's country and they hadn't bothered to inform me.
It was the last straw.
I had a long chat on the phone this morning to the director who pays my invoices and what he had to tell me was not good. It underlined that my desire to walk away was right and the director was fully supportive of my decision (what I've been through is beyond the director's control).
So I composed a firm but polite email to the department abroad, explaining why I was quitting. Half an hour later, they sent me more work! I did it, making it clear that would be the very last piece. The company is in a mess and I have no wish to be caught up in the internal politicking.
And, whaddyaknow! As I quietly shut the door behind me, another one opened when someone who'd enquired a month ago about offering me some copywriting work rang to say they definitely wanted to hire me. Result.