OK - consider this sentence:
If I'd have had the money I would have bought it.
Here in the UK, that would be a perfectly reasonable sentence, and so
far as I know, grammatically correct. "I'd" is short for "I had", so
"I'd have had" expands to "I had have had". I've been hearing, using,
and reading, this construction for decades, and no-one's questioned it
until now.
Now an American tells me that "had have had" is wrong. If I had to
guess, I'd guess that they were looking for "If I'd had" instead of "If
I'd have had".
Google certainly confirms that I'm not alone in my use of "had have
had". The question is, can this usage be backed up in any formal
reference? Or is my American friend right, and I've been getting it
wrong for nearly half a century?