That's useful. I was definitely going to have privacy glass but you have me thinking. I normally have privacy glass then get the fronts tinted a light smoke to lessen the delivery van effect if you know what I mean. But even though the fronts are always the lightest tint I can get, they are almost certainly illegal. I must get away with it because the light upholstery in our Range Rover Sport and previous BMW X5 made the interior easily visible. The police are more concerened with limo tints (and what's going on behind them, probably). We have an A6 Le Mans with the S-Line interior (black and more black) which does appear to some people to have tints. I had always put this down to the contrast with the bright red bodywork but I can see how your similarly dark interior might make the standard glass appear darker just as my light interiors made darkened glass appear lighter.
Given the choice, I would prefer it if the S-Line Q5 could be had with a light interior; maybe the silver or beige leather. The A6 is quite oppressive at times with even the headlining being black (or anthracite if you must) and no sunroof. I'm semi-persuaded that having a Q5 with the panoramic sunroof would reduce the effect but I'm nevertheless a bit miffed that the same Sports seats can be had in the base car or SE in a variety of colours while S-Line customers have to stump up a couple of grand for 'Exclusive' trim to get any variety. Maybe I need to stop being spoilt and make a double saving by sticking with the black interior and, as a result, unticking the privacy glass box!
What you've said about Brilliant Black is exactly what I'd hoped to hear and makes me wonder why metallic blacks even exist - certainly at extra cost. I've just spent the evening with my goddaughter after breaking the news to her that the insignificant looking damage to the rear wheelarch of her Renault will probably mean she'll have to pay for the whole rear door and three-quarter panel to be painted because of her greeny silver metallic/pearlescent finish. Fair enough; she likes the colour but black is black isn't it? I had a small but unsightly scuff on the X5 which resulted in half the side of the car getting resprayed just because it was a metallic black. And it was still never a perfect match!
All of which brings me to another thing I'm considering . . . . paint protection film. Maybe because I live in London, no cleaning day goes by without the discovery of new stonechips or parking dings and scrapes. The other day I saw a lady squeeze between two cars in Sainsbury's. On closer inspection I could see her jeans had left a line down one of them. It would probably polish out but it showed how easily and innocently damage can occur. I know they can cover vulnerable panels or whole vehicles but I'm not aware of ever having seen a car that has been treated. If the penalty for having this protection meant losing some of the deep 'wet black' gloss you describe, I don't think I'd bother. But if it really is as difficult to detect as the ads would have us believe, I'd be very tempted.
I wonder if anyone has any experience or thoughts on this.