Captain Universe No.1 appeared in 1954 by The Arnold Book Company, a publisher based in London's Piccadilly. It was drawn (and perhaps created?) by Mick Anglo, who that same year had created Marvelman. There were similarities to Marvelman too, with Captain Universe's alter ego shouting a magic word to transform into the hero, and the character's seemingly infinite powers.
Here's the story to read for yourselves. It's a strange dreamlike tale with random occurrences and a cheery disregard for basic science. Captain Universe himself proves to be quite brutal, who ends up destroying an entire world! "It was a hard decision to make" he claims, even though we've just seen that it clearly wasn't. As for the 'Horror Plant' of the title, - it appears in just one panel and the Captain dismisses it with "G'wan! Lay off!". Some horror!
Other stories in this 28 page comic feature Lt. Mike Miller of Homicide and a Western with Rocky Colt and Red Feather. Here are the opening pages...
There's also a one page True Space Facts page by Denis Gifford, who seemed to be in everything in those days!
One thing that Captain Universe didn't have in common with Marvelman was longevity. Issue 2 was the last. However, he did turn up decades later in a cameo appearance in The League of Extraordinary Gentlemen by Alan Moore and Kevin O'Neill, as seen here.
You can read the story from Captain Universe No.2 in the book Great British Fantasy Comic Book Heroes, published by Ugly Duckling Press.