Hi Graham,
Notation Composer is exactly what you need
You can play on your keyboard (MIDI connection) and record into Composer. It will then give you sheet music for your performance. There's a new feature in the latest release that allows you to record without using a metronome or other beat marker. You can then adjust the barlines/timing after you record.
You can try it out free for 30 days by downloading the trial version. Unlike other software, the trial version is fully functional for saving, printing - everything. You can get it from
www.notation.com/NotationComposer.php
If you have any questions or run into any problems, just let us know.
ttfn,
Sherry