I’d agree the sandwich board looks to be a major part of the problem. It’s pretty much directly in the driver’s line of sight as he approaches the white lines (look where driver’s head is vs. the sign in the still) and you being of narrow frontage would have been completely obscured for much of the last few seconds of your film.
A car with a longer bonnet (Mondeo, S-Type Jag, bigger Beember, Vectra etc etc) would have needed to get to where that Beemer’s bumper did just to see past the sign.
Definite word with the board’s owner and if they don’t listen show the local police the video.
Doesn’t excuse the driver but you can see how it could happen.
Assuming no following traffic if you had moved over a bit towards the middle of the lane (especially given the curve on the road) you would have been more in his field of vision.
Not criticising just trying to suggest how you might avoid a repeat.