This was really nice to listen to, Nigel.
You got the whole "Easy-Listening" style going here and it makes for a pleasant rendition of the song. I kept having images of Disney movies go through my head while listening to this, so I'm not sure what to make of that - especially the higher bits.
In terms of what to improve on, I don't have too much to comment on but I'll give you what there is. Right now, your interpretation falls flat because, as an improvisation, it really doesn't say much of anything about YOU. It retells the piece as you intended to, but it lacks personality in terms of the arrangement. Your performance is what gives it character now - it's very well played.
So the next time you do an improvisation recording, my suggestion to you is to be more free about it. Let the music take you where it wants to go and don't necessarily return back to a theme just because it's your "main" one - see if any new ones come up and then play around with those. Don't limit yourself: the whole point of improvs is usually to have them be nice and freeform.
Anyhow, that's my two cents. Very nice interpretation
Keep posting!