If you mean WW2 bomb sites, I think they'd all been redeveloped by 1974. I remember as a kid c.1960 going into Manchester with my parents, and being told that derelict sites were bomb sites from the war, but I think in the mid-60s there was a big push to finally get rid of the last remaining ones.
I lived in Liverpool in 1973/4. There was a Victorian office building near the docks which was intact and in use, but it had some quite large chunks missing from its brickwork, which I assumed was caused by shrapnel from a nearby bomb during the war.