I have been pestering Hornby to re-issue these for years since their attempt to test the tooling was in good order. Despite my contacts through Antics, no-one ever came back to me. When Airfix originally made the 1/1200 kits, they used the same masters that they had originally made the 1/600 kits. From memory, the master models were of a larger scale than 1/600 (1/500 + something) and when it came to going down to 1/1200, some of the smaller kit components (Anchors etc.) were too small to be made separately and Airfix decided to omit them rather than add them to a 1/600 kit of the hull component and use that for the new master. The Bismarck and the Tribal class Destroyers have hulls that are too deep because the line was drawn too far down the full hull master model. Indeed, the Tribals show some of the bilge turn in.
Finally, they only made models that they had models in 1/600 at the time, and there were already the Cassadio (now Revell) 1/1200 KGV class in the market, so they saw no need for duplication.