yes there were several incidences of German aircraft landing in the UK, some pilots actually thinking they were landing back in France! the one story that always makes me laugh is the story of a He-111 that landed on an airfeild and upon realising their mistake in having not landed in france, managed to turn around and take off again- meanwhile the RAF personnell were on the blower trying to get permission to shoot at the aircraft
as for us using German aircraft i'm in no doubt it happened, but it's all very hush hush if it did because there aren't many accounts of it happening.............
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"Reminds me of the time I sank the Tirpitz" comments a Spitfire pilot, "One pass of course, old boy."