Thanks... I removed the platter, then had a look on the bottom of the deck... it took some finding as it was in an obvious place under one of two screwcaps right by the anti-skate
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After listening to the last minute of BA Robertson's
Cool in the Kaftan about twelve times, and adjusting the screw this way and that, trying to fathom which way is what, i thought I'd have another look under the other screwcap by the anti-skate, and with the arm in its cradle, the actual adjuster is revealed... got there in the end