Killing Ground by Steve Lyons

Imagine you can live a life completely free from pain, from aging, imagine you could live forever without fear, without losing control, without ever being sick. You can see things with total clarity, unfettered by any irrelevant details.

This is the Cyberman's legacy, the promise they give, the only thing you lose, your freedom, your self.

Arriving home on Agora, the Doctor and his new companion Grant find the planet in the thrall of one of his oldest and deadliest enemies, The Cyberman.

A breeding colony has been setup to propagate their race, the Doctor is captured, languishing in a cell at the mercy of his evil overseers. All hope rests with Grant and the freedom fighters he has joined as they work on a desperate rescue attempt...