England needs to control the land that the railroad runs through, can't just have open borders. There are three ways to do this: colonization, diplomacy, and war.
You will need to go to war with the Zulus and Egypt at least. Buy up any city-states along the way, use settlers to fill in any gaps and buy tiles when near competing civilizations.
I allied with and then married Zandikar and Mogadishu even though they were not required for my railroad; they made some of the best trade routes with Suez. If you do this, move your Ship of the Lines to the gulf to protect them from barbarians.