Well thanks to one and all for the replies. In the end I plumped for a G&L L2000 tribute which should arrive tomorrow. Family commitments mean that I can't make it down to Bass Direct so I rolled the dice with a brand I'm more familiar with. I have a cheap Yamaha 5 string which I hardly ever use but tbh the B string was messing with my 'the lowest string is an E' mentality.
But today, after over 30 years of 6 strings I finally saw the light - big time. I loaded up a few drum loops and just played a few simple bass lines over the top. And an hour later I was still there, improvising & developing the groove, trying out a few novice thumb slaps on the neck, seeing how the melody could alter and morph around the beat, getting ragged fingers (on my right hand? Mad!) and more to the point, connecting with the rhythm and feeling it all in my gut in a way I have never done with a lead guitar. Don't get me wrong; I love my - what do bassists call a lead/rhythm guitar? But lead guitar connects with the bit of me that wants to sing. That bass I'd ignored for so long connected with the bit of me that wants to dance.
So, at the weekend the old Yamaha goes back to the person I'd bought it from to help them out with cashflow. But tomorrow the G&L is due to arrive. Tomorrow is going to be a good, good day. Oh; and the time I've spent recently on the Bass Direct website, leering in wonder at the things you all already knew so well...