Are you sure you are all in order now?
A 'very standard half acre site' would measure approx 30m frontage X 67m deep. If this includes half the road (@8/2=4m) and a small farm road (@3m wide) all along the depth, then the 'net size' of your plot would be 27m X 63m = 1701 sq m = 0.1701 ha = 0.42Ac.
In order to end up with a little over a third of an acre plot the public and farm roads would have to amount to 0.15 acres = 607 sq m which would give them a "halfwidth" of 6m if you know what I mean. Ie the public road would be 40 foot wide and all the farm road would be 40 foot wide.
Are you sure??? Also heed Scotty's advice on minimum tolerences for wells, septic tanks and buildings etc