The British certainly helped us, but we were still nowhere near developed when they left. We were poorer than the world's average when the British left in the late 1950s. Literacy is only 52% in 1957 as many adults were illiterate migrants from China, India and Malaysia.
We certainly wouldn't developed today if we just 'continue the age old tradition' of our seaport business during the British times. The entire transport and storage industry makes up only around 8% of our GDP, and that it includes airports, post and courier, warehousing and storage, and other forms of transport. Our largest industry is actually manufacturing which makes up 20% of GDP.