...new towns built to absorb overspill from nearby cities. [+ from]

为吸纳周边城市的过剩人口而兴建的新城镇

...overspill council housing.

安置城市过剩人口的市政住房

There is often overspill, with the office piled high with parts and the shop jammed full of goods waiting to be posted out.

东西常常多得无处存放，办公室里零件堆得老高，商店里也塞满了待寄的货物。

With the best seats taken, it was ruled that the overspill could stand at the back of the court.

最好的座位已经有人坐了，按照规定，没有座位的观众可以站在球场后面观看。