I have rung them on many occasions and usually they connected me to a TP in a few minutes. Could be a good excuse to have a glass of wine during the day though
If you're like me and don't have the patience to wait for the Duty Planner to call you back, download the development plan for that council and everythings in there.
Depending on zone/policy area, on 405m2 we could probably squeeze 5 on there if its in an ideal policy area or maybe its a policy area that has a min site area of 400m2 in which case you would only fit 1.
But with the frontage of only 10 that will really limit it down to either 1 or 2 (like a duplex/semi detached type arrangement).