Finally saw Hammer's The Quatermass Experiment (1955), and wow, what a hatchet job they did on Quatermass. From the voice of reason of the original BBC serials, he's become a loud, bullying American, who gets to boss everyone around just because he can raise the biggest volume. There's an interesting subtext, in that he's both the guy who creates the whole mess and the man who deals with it later (and, even later, tries to do it all over again), but that seems more confused than anything (why, after all this, would anyone allow him near a scientific facility again?) and an accidental side-effect rather than something thought up to help explain Brian Donlevy.
It does have its moments--that scene behind glass, of the patient getting up to molest a bunch of flowers, or the girl playing dolly while the monster walks up behind her, or the scene at the zoo the morning after...those moments retain considerable power.
But that ending (SPOILER), lifted from Hawks' 1951 The Thing--I guess they figured if electricity was good enough to cook an aggessive carrot, it was good enough to fry an oversized cactus. The film in turn went on, I suspect, to influence the 1958 The Blob, where yet another alien went about absorbing other life forms.