I suggest you check out wiki as an introduction to the history of the hovercraft's development. Hovercraft - Wikipedia, the free encyclopedia

Another one would be Hovercraft history.

The website MilParade.ru | #32 | Levkov*s Hovercraft has an article on Soviet research on the hovercraft's military applications. I concede that it was the Austrian Hungarian navy that first looked at some form of hovercraft in the pre-WWI era but they didn't continue it. The Soviets in the 1930s made an effort and did produce some craft. However with Germany rampaging across the countryside, the development was still born.
It's unlikely, though, for the Germans to have developed hovercraft for crossing the Channel to invade England. Even if German pilots did prove the existence of the ground cushion effect with the Dornier aircraft, as far as I have checked, the German research didn't dwell into hovercraft.
The modern-day British inventor recognized for the development of today's hovercraft is lucky that the Soviets had such a penchant for secrecy.