is it only the 79 and 20 that serves the whole of Hall lane estate? I remember when Ok travel had service 156/177/178 and Northern had service  (141/157 (493)/159 minilink series) and X62. Also service 148. hopefully service 238 will go into the estate where the 79 operates, its quite a big estate, its been awhile since been in that estate unless the council has started to knock houses down. Since Phili depot got shutdown and Northern streamlined their bus services.