yep North head would be the closest. I swear there used to be a map on the bom of where all the stations around sydney are but i just looked and couldn't find it. i thought it was below the observations??? In bay, when it is reading 10 knots gusting to 15 at the airport it is generally about 5-7 at dolls. Saying that, sometimes when it reads 22 knots gusting to 27 it seems about right. Generally it does read higher than it is and i think there is usually less wind up at narrabeen than there is in the bay so you can look at the airport and harbour readings as well and make the call whether it is worth the trip to the beach from there.

Here is the link you want showing the stations. Click on the station and it shows you the last 72 hours of wind.
http://www.bom.gov.au/weather/nsw/nsw-observations-map.shtml

for a better site,
go here as all of the columns are sortable so you can see where the wind is highest or which has largest gusts

www.weatherzone.com.au/observations/observations.jsp?state=NSW&type=metar
it is also good for qld and other states.

Thanks!! Great sites.