Hi I've attached a screenshot of what I'm seeing. Inserted new Track which seems to be receiving sound from the SoundCenter panel (as in, I can see the levels monitor react when I press the synth keys); when I hit R to record I get a metronome sound and can hear the synth but nothing gets recorded. Somebody please tell me what I'm missing, as as far as I understand from the in-program Help when I start recording it should create a wave clip. Thanks.

One thing missing in your illustration is transport controls.  Did you hit the record button in your transport? The record icon on the track just arms that track for recording.

This is a very common source of confusion for beginners.
You cannot record using the keyboard in the Sound Center GUI. It is for auditioning and triggers the sound internally. It bypasses the input stage where the notes would actually be recorded. This is true of any soft synth with a keyboard in the GUI.
You have inserted Sounter as a Simple Instrument Track. This is actually two tracks in one, the MIDI source track, and the synth audio output track.
In the following screen shot, I have inserted Sound Center with the two tracks split out.
Track 1 is the synth audio output.
Track 2 is the MIDI input. This is where recording would happen.
If you have a MIDI controller connected, you can record the notes realtime to this track.
Or you can enter notes to this track using the Piano Roll View.
Note that the synth Audio Track does not have a record button.
When you play notes on the synth GUI keyboard, the sound goes directly to this track, and cannot be recorded.
Hope that makes sense.

Thank you! I think I've got it - at least I've managed to turn sounds from SoundCenter into notes and then a waveform in the track, which is a start.

What you CAN do is have Sound Center function with a midi track for a controller, and key in the notes manually. It may not be fast but it's super effective. And accurate every time. The simple fact that I can do it at all is what drove me to cakewalk in the first place... 13 years ago.