Stop press – I’ve found it.
Somewhere along the line, the video file had a “glow” effect on it. I rebooted everything again and it showed up in Media FX.
Not sure how this happened (I am absent minded sometimes, but I’m not stupid), but it looks like it’s solved the problem. Sorry for anyone racking their brains on this already.
Thanks,
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One of life’s eternal optimists
West Midlands, UK
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