Hello again,
Well, despite Rusty's dire predictions, I did make it through to stage two, but have not got any further, sadly. I haven't had any feedback yet, but I pretty much know where I went wrong: the parts of the aptitude tests that involved using the joystick. Nerves affected me in the first test and I kept moving it all over the place, even in the wrong direction at times, and I had only just got used to how sensitive it was by the last attempt.
I was always going to self-sponsor, but I will wait until I get any feedback before I press onto the ATPLs under my own steam. If it turns out that I am way below the standard, I guess that this would be a good opportunity to review my options once more.
I am going to post my own description of what was involved here when I've had a chance to calm down a bit, because I think it really does help to know what you're in for. Thanks to everyone who gave me advice!