Gary, Peter: Many thanks for your help so far!
Re:
>I can confirm that the mirror locks up immediately you switch to S or C.<
For me, the mirror doesn't move when I turn the switch (whatever position the mirror is in, whether up or down, and however I move the switch).
Re:
>If you set the switch to S, the lever will return to N when you wind on after taking the shot.<
This doesn't happen. The lever does not return to N. It just stays wherever it was.
Re:
>If you set it to C, the lever will not return to N and the mirror will stay locked up. To stop this you should set the lever to S or N before winding on and the mirror will come down as you wind on.<
The mirror comes down as I wind on - but then jumps up again immediately the shutter gets to cocked position.
The complete sequence I am experiencing is that with the shutter cocked, the mirror is permanently up (so I cannot compose a shot with the shutter cocked; is that how it should be?). After shooting, as I wind forward, the mirror returns to position, and I get what is (what I _assume is) a faithful 6x6 view through the viewfinder and the lens... *but*, the mirror stays in this position only while the shutter is not quite cocked. At this stage the shutter will not fire. As soon as I wind on that last bit such that the shutter is cocked - such that the shutter will fire - the mirror jumps up with a loud clap and I have no viewfinder view. This happens whatever position I set the mirror lock-up lever to - N, S or C. And winding on does not cause the lever to reset from S to N.
Is the above behaviour normal, or does it sound like the camera has a fault? Or could I still be doing something wrong? (I would be really pleased if it were my mistake rather than the camera's, but I am finding the behaviour v hard to reconcile with expectations / with the instructions!)
_Many, many thanks for all help.