The Clash 3rd album - aka an LP - came out on 14th Dec 1979. I listened to it for the first time a week later on 23rd Dec. Full disclosure: my brother won a copy at the Slough College disco the night before. As a double album, I think it might have cost £3.99 or so at Smiths, Boots or Our Price. Maybe more expensive?? Ha! Get along! Get along!
I saw them at the Crawley Leisure Centre when this album came out and they were superb. I bought a shop display sized poster of the album cover in the foyer afterwards. Had it on my bedroom wall for years but somewhere, along the way, it has disappeared.