Thanks to Mike Fantham and
FlyQuiet for the following.
North Korean flyers won the Wakefield Cup (F1B) twice in 1975 - Piak Chang Sun - and 1977 - Kim Dong Sik. They flew models that looked like the one in a picture I found on the internet.
Type, 'Kim Il-sung Stadium, Pyongyang, North Korea', into google maps - zoom in, choose 'photos', and enlarge the pictures along the entrance road to the stadium.
There are six sports represented by the six statues in that area. F1B is one of them.
I also did some Googling and found "World Free Flight Review 1976-1978", which included a report, from page 61 onwards, of the 1975 Wakefield World Championships.
Page 84 onwards of the review has a report of a fog and ice bound International Coupe competition at RAF Halton.
I was able to read these reports from "World Free Flight Review 1976-1978" as it is on sale at Scribd, which offers a selection of pages for browsing as an incentive to buy the actual book.