In the 1980s a local newsagent used to give me his trade magazines after he'd read them. One such publication was this issue of Profitable Newsagent from April 1984 which featured a four page article on the state of British comics at the time.
As you'll see when you read the item, the feeling was that, although sales were declining, comics were still a healthy investment for newsagents. Apparently combined sales figures for comics in 1982 were £45 million.
The article makes an interesting observation about content: "Very often, adults were swayed by a nostalgic appeal and a reminder of the type of comic which they themselves used to read when they were young. But unless it also appealed to the child who would receive it, future sales would be lost". That remains true to this day, which is why pandering solely to nostalgia serves no purpose if it fails to excite the intended audience. Comics must reflect modern tastes, but at the same time appeal to the parents who purchase them. It's never been a simple task to balance the two but it's what has to be done.
As for displays back then, comics were usually on wire racks, as can be seen from the photo above. "Most place comics on lower shelves where they are easily seen by younger children" informs the article. Sadly, a practice not always followed today, with some news chains bizarrely putting comics well out of the eye level (and reach) of their intended audience!
The circulation figures of 30 years ago are far healthier than those of today, although it should be noted that the average 1984 figure of 100,000 a week was easily half the figure of 30 years previously. Comic sales have been dropping steadily for decades, as each generation becomes more preoccupied with other distractions.
The saddest thing is that of all the comics shown in the cover photo, only The Beano has survived to this day. (Poor School Fun barely made it past 30 issues.) A similar photo today would show untidy shelves full of children's magazines for the very young, bagged with toys, with little chance of kids being able to flip through them as they were doing in this image. (Although Beano is still rarely, if ever, bagged now.)
Click on each page to see it larger (and you may need to click on it again to see it even bigger).