is it possible to only show products £1000 or under across an entire shop? Or is there custom XML code you can apply on a per category basis?
You should add a filter in product collection like this:
$collection = Mage::getModel('catalog/product')->getCollection() ->addAttributeToSelect('*') ->addAttributeToFilter('price',array('from' => 0, 'to' => 1000)) ->setPageSize(5000);
You should rewrite
Catalog/Block/product/List.php to custom
Follow this link: How to override core catalog block product list?