My mum was a piano teacher, so from about the age of 6 I played piano...
Then I heard "Hit me With Your Rhythm Stick"... And a bit later I went to my first proper "big" gig, Ian Dury and the Blockheads closely followed by The Clash on the London Calling tour and realised that bass was cool.
Then in 6th form we got a band together (me on keys) with our RE teacher to play some Barclay James Harvest and Dylan stuff as a pre-amble to a school showing of "The War Game" and Mike played on his brother's violin bass (it's your fault, @lurksalot!), which was the 1st bass I got to play.
I gave up the piano, went to uni and got into The Funk; my flatmate had an old acoustic guitar with the two top strings broken so I used it to jam along to Bootsy and Parliament. As soon as I could play something vaguely funky I got together with the boys from Chestnut Avenue and we formed A Band - Dredd and the Badass Weeds and within a week we were gigging, me having borrowed a short-scale Gibson off Jez (later of MDMA then The Utah Saints). And the rest is history! They went off and had lots of musical success, while I moved to London and formed a bizarre punkfunk band who liked to dress funny.