Wonders of the Spaceways No 1 (Nov 1950) featuring “Convoy to the Unknown” by D. R. Mencet (aka John F. Watt). Cover artist unknown.
Book cover or magazine cover? 1950s British scifi was more often published as a series of paperback books and not as magazines or digests like in the US. Wonders of the Spaceways was published intermittently (no set schedule) from 1950 to 1954.