There have been a fair few ZX Spectrum games based on the Alien franchise, including 1984's Alien from Concept Software/Argus Press, Software Studios' Aliens: The Computer Game (UK), and Activision/Mr. Micro's Aliens: The Computer Game (US), but none of these went down the obvious horror platformer route, which is a bit of shame in retrospect.
Nevertheless, thanks to a group of homebrew developers, you can finally play something akin to that experience on a ZX Spectrum 128K, in the form of Aliens: NeoPlasma — an impressive-looking homage to the Alien films (as reported by IndieRetroNews!). It features everything you'd want from an Alien tribute, including xenomorphs, face huggers, and grim, industrial-like environments, but follows a wholly original story that's distinct from the films.
Aliens: NeoPlasma is the work of a three-person development team, including programmer and level designer Alexander Udotov (aka Sanchez), musician and sound effects artist Oleg Nikitin (aka n1k-o), and graphics and scenario writer Evgeniy Rogulin (aka ER). They are responsible for creating the ZX Spectrum 128K tribute to the Alien films and have also made an improved version of the game for ZX Spectrum NEXT taking advantage of the superior hardware.
According to IndieRetroNews, these games have been available to buy for a while now, but have only just been uploaded to itch.io over the last six days. So, if you want to pick them up, now is no better time to get them for free.