My strategy (which is questionable) is to do 2 cities outside of the main centre of the map where paddington, kingston, lewisham and newham are then go inside the centre and visit two towns in there then back to crawley. This would be used for the first 2 buses.

For the third bus i did the big trip from the top of the map to the bottom of the map because they are long journeys therefore i couldnt put in anymore towns.

The last trip i left guidford which is close to crawley then the other two towns on the south east coast. This proved a good solution becasue southend and canterbury are fairly close to eachother and with guildfore being very close to crawley the journey time was prefect.