On the last: if you find your tourer roller blind seems to have failed, it migh be as simple as a trapped bit of gravel. No idea how it got there, but hol,ding the handle on the ground with my feet and pulling the mechanism upawards released a bit of gravel and it works perfectly again now.
On the challenging side, I upgraded to a a full BM54 flat pin version. I struggled because I could't get any audio from the TV / aux input,though nav worked OK. It turns out the BM54 I bought can take stereo audio in for the TV. Good news if you have a Freeview tuner!. I've also from info found on the net got an aux in on the new BM54 to use for my DAB radio, though the DAB radio itself is performing really badly which made me think it was all not working right. At the same time, I've come up with a way of creating another aux in that will work with any of the hiline radio units (BM54, BM54 back, BM24) by using the cassette player audio circuits. To be fair, I have been screaming at the car a fair bit when things seemed to work them stop working, when it turned out to be DAB signal problems!
Finally, I've found a way to relatively easily use the existing TV aeriels for a DVB (freeview) tuner. TV reception where I live is pants without a good rooftop aerial, and I currently only have one of the two screen antennas fitted, but it's working well enough to be worth others trying to confirm when I get time to write it up!