Can “unless” be used in unreal past (with would have)?

Question

I found conflicting information about the subject: BBC World Service states that:

And we cannot use unless with would to talk about unreal future situations:

• If he didn't take everything so seriously, he would be much easier to work with.

• If he weren't so bad-tempered, I would help him to get the work done.

We cannot use unless with would have to talk about unreal situations in the past either:

• If you hadn't driven so recklessly, you wouldn't have had this accident.

• If you hadn't had that last glass of wine, this would never have happened.

While Education first website shows usage in all conditionals. What is correct then?

Why I cannot find anything about this usage besides that BBC website?

Answer 1

Here's another warning against usage of 'unless' for impossible conditions:

https://dictionary.cambridge.org/us/grammar/british-grammar/conditionals-and-wishes/conditionals-other-expressions-unless-should-as-long-as

As for Education First vs BBC, the former is Sweden-based (according to Wikipedia). Not sure if the usage of 'unless' differs in AE though.