Doctor Who The Ark In Space.

4 part 25 minutes adventure. The second Tom Baker of season 12

The TARDIS lands on a space station orbiting Earth in the distant future. It's seemingly deserted, but the Doctor, Sarah and Harry soon discover that they are not alone. Thousands of humans are in cryogenic sleep, and while they've slept their Ark has been invaded. A parasitic insect race, the Wirrn, have taken control and threaten the very future of mankind