This question is about a mild form of a specific speech pathology that seems to be gaining prevalence in Australia and if there is a term for it. It is not an "accent" issue, because it can be found in many flavours of Australian accents.
I called it a "lazy L" - here's what it is...
When pronouncing "L", whenever the substition would not make the word ambiguous and where the “L” lies neither between vowel sounds nor at the start of the word, instead of making an "L" sound (where the tongue is held to the alveolar ridge), the tongue remains immobile and instead the lips are slightly pursed making a vowel-like sound that in English is sometimes written as "ooh" (in the sense of experiencing mild pain, such as stubbing one's toe).
For example, "mental" is pronunced as "mentooh" and "girl" as "gehooh". The sound is similar to a leading "w" sound. It's not a pursed as the German ü. Perhaps similar to the end sound of the American "eew" exclamation of disgust.
So, what is the formal name of this substitution?