// ==UserScript==
// @name           Gumtree Google Maps
// @namespace      http://alf.hubmed.org
// @description    Rewrite Gumtree links from Streetmap to Google Maps
// @include        http://www.gumtree.com/*
// ==/UserScript==

var a = document.evaluate("//a[contains(@href,'http://www.streetmap.co.uk/streetmap.dll?Postcode2Map')]", document, null, 0, null).iterateNext();
var c = a.href.match(/code=(.+?)&/);
if (c){
	a.href = 'http://maps.google.co.uk/maps?spn=0.01,0.03&q=' + c[1];
	a.setAttribute('target', '_top');
}