Ive recently taken a gamble on a cheap silnylon tarp from germany that I found on amazon for £35 delivered. It arrived today and I'm pretty pleased with it. Here are the details
http://begadishop.com/catalog/product_info.php?cPath=316_318&products_id=5458
http://begadishop.com/catalog/product_info.php?cPath=316_318&products_id=5458