Even though this will be incomplete in a couple of years due to Alien 5 and Prometheus 2, £10 for all the Alien films (eight discs) on Blu-ray is very cheap.
Prometheus to Alien: The Evolution Box Set 8-Disc Set 1979: Amazon.co.uk: Sigourney Weaver, Michael Biehn, Lance Henriksen, Winona Ryder, Noomi Rapace, Tom Skerritt, Paul Reiser, Charles S. Dutton, Ron Perlman, Michael Fassbender, Ridley Scott, James