Thanks Windy!
I didn't record the next couple of steps as they were boring - essentially just playing the triads over the backing track, and then, once happy with that, adding in the sevenths.
That got me to this stage - improvising using the melody, the occasional root note (again, to prove to myself that I know where I am), and now some of those arpeggios.
Still a long way to go, but the path appears to be a good one, thus far...
https://youtu.be/R6wcpTxMIkICheers
Derek