Return rows where field contains non alpha-numeric characters

I am trying to extract all rows which contain a non alpha numeric character at it's most literal except allowing space. Any punctuation, brackets - square and round, currency symbols etc.

I have tried to adapt the advice as given here Return sql rows where field contains ONLY non-alphanumeric characters however using not LIKE '%[a-z0-9]%' returns rows with a space. Fine. I amend the regex to be not LIKE '%[a-z0-9 ]%' and I now have zero rows returned. What am I doing wrong?