[Johnno]

I like Fluff actually enjoy mowing and will say I am pedantic about it... you must always do the edges first, then the lawn.

If there are bindi and other weeds, you don't need to spray with chemicals, put your mower on the highest cutting possible, let the lawn grow and grow and grow, let it go to seed, yes it will look crappy and shaggy, when it has turned to seed, get the mower and catcher and mow it (at the highest deck setting) basically just taking the top and seeds off.

Repeat for half dozen mows or until the bindi and weeds are gone. 

Here now is the trick... maintenance of the lawn must start slowly, drop the deck height by two, use the catcher and mow (remember to do the edges first). Inspect the mowed lawn for any bindi and weeds, if gone, drop the deck by one lower again. 

You don't need to use the grass catcher now, by letting the grass fall back you are essentially feeding your lawn. 

From here on out you do not want or need to mow your lawn to dirt  by mowing higher the bindi and weeds can not thrive, they require sunlight so with a higher and thicker lawn you have controlled the bindi and weeds.

done... there is nothing better than to sit back with a whiskey and dry looking over the freshly mowed lawn not to forget the smell of freshly mowed grass, yup satisfaction for a job well done.