"x more than y" means "y + x" - a sum. "x% more than y" means "y + x% = y + y×(x÷100)" and "x% less than y" means "y - x% = y - y×(x÷100)".
To me, "x times more than y" means the same as "x times as much as y" only "y×x" and "x times less than y" means "y÷x". I guess this might seem ambiguous if you bracket the expression like "x times (more than) y", but in practice it's bracketed like "x (times more than) y".
I try to say "{x} is ten times {y}", which is, as far as I can tell is unambiguous. (Mostly, what's ten times colder?)