StevenUK - congrats on your new X3, looks really nice - I still haven't seen a DSB in the flesh. I may be getting those alloys for winter tyres and I like them every time I see them.
Re. DVD volume, I don't think it can be adjusted and it's DANGEROUS! The difference is ridiculous. BimmerUK76 had a thread on this.
Re. USB, just to confirm what other people have said, it should work with any size so worth trying a different stick. A USB stick is preferable to the Music Collection which has a lot of flaws. I bought this one which is cheap as chips and had been working well for a few months. I would personally stick to solid state unless you need the extra capacity
https://www.amazon.co.uk/7dayshop-Me...9963776&sr=8-1