Graham UK,
I highly recommend learning manual bass - your playing quality will really improve. Pick some easy rhythms like those slow 8 beats. Then slowly learn the others. Your keyboard arranger is a great learning tool too. I learned many of my bass lines from my own arranger. At first, I just concentrate on the bass lines and not worry too much with my right hand and try to follow a song with simple bass lines from CD/tape. Don't start with walking bass lines - those are for more advanced players. It's like learning to ride a bike, you'll get used to it after a while.
-Han