paypalwpp.php inserts a shipping address outside the zone definition, no tax applied

[torvista]

For the record, the offending bit of code that was setting the zone to 0 because there was no match:

if (!$zone->EOF) {// grab the id
   $zone_id = $zone->fields['zone_id'];
   } else {
      $zone_id = 0;
   } 

I could have defaulted this to be the customers shipping address zone but since I make everyone register in my shop I'll stick with the above sledgehammer approach for now, why should I allow Paypal to create addresses willy nilly?
I'm suprised no-one else has had this issue before...?