Result - kudos to Mr. Foxen and Shockwave. Thanks guys.
Popped up to Kingswood today and there was indeed a Squier VM J-Bass '77 in black there, in as-new condition (really - I couldn't see a mark on it anywhere) for £175.
There was also an older Yammy in natural finish (which sounded nice, but the action was a bit too high on the upper strings for me) for £95, and a black Ibanez for £115 (good nick, but had a slightly noisy tone pot and the intonation was out on the bottom string - all easily fixable).
But for me, the action, sound and condition of the VMJ just blew the others away. Really liking the maple inlayed neck too.
Bit more than I was intending, but he chucked in a strap and for what is essentially a new VMJ, I can't complain at all.
Have to pick it up tomorrow as was on the minibeast today, and strapping the VMJ to my back didn't seem like too good a plan.
Can't wait to get it home and start practising on it!
Cheers again all...