I never bought any of these cover albums, though I can recall seeing many of the LPs in stores. (I was such a soundtrack snob in those days! Only the OST's for me.)
But looking at them now, especially that back cover picture of Barry at the door, I get all tingly and nostalgic and regretful that I never picked these up at the time!
Quick ramble here - I too remember that I knew very little about the film itself when I bought the double LP, and being disappointed that it wasn't electronic. I wonder if I'm the only person in the galaxy (this one) who was actually slightly disappointed when the opening fanfare blasted out of the speakers.
Of course, when I saw the film, it became an almost magical experience.
Everything you said.
I was 15 and thought the MECO single was from the film. Having no money I ordered the LP through the lending library, unbelievably they got hold of it before it was released in any stores in my home city and I went back to the library just as they received it. First listen was very disappointing, by the time I took it back I was totally in love with it, saved pocket money and had the soundtrack a few months before the film was released. I don't remember how much longer it was before I finally saw the film but going by other peoples research I'm guessing it must have been Dec 77-Jan 78 here in the UK.
Shortly after that, my Mum gave me this London Philharmonic knock-off from Woolworths, which I still enjoy for its 'Stereo Space Odyssey-odyssey-odyssey' on Side Two.
Me too Dog. Original tracks by Douglas Gamley. ( I tried to find examples on YT with no luck ). I didn't care for the weak Star Wars recordings on side 1.