I cant imagine they will deny your buyer from bulding a house, otherwise the land would not have been approved to be split in the first place. They may ask you (or the buyer) to change the design from the original plan that was approved in 2002, but i doubt they will say no altogether to building a home there.

As far as i know, all you can do is wait, but i have a feeling if the council has something to do with it, you will be waiting for longer than 3 weeks…