I have a S bar Brompton and I am also about 1m79. The S bar fits perfectly.

But you should also look at the saddle position.

The Brompton pentaclip on which the saddle is mounted allow for two positions in height and two positions in length. To have enough distance between the saddle and the handlebar and not being cramped, you need to put the pentaclip behind the seatpost (saddle rearward in the picture below).

With 1m79 and short legs, putting the saddle on the highest position in the pentaclip should allow you to use the standard 520mm seatpost (but this depend also of the saddle height and pedals thickness).