Just had a look at the PAH site and they are doing free delivery on all orders, normally it's free on orders over £50.
Free Standard Delivery Terms and Conditions
1. Offer ends 9am 29.06.09.
2. Offer applies to Standard Delivery to one UK address.
3. Offer excludes Express Delivery.
4. Offer does not apply to any purchase of personalised gifts made through Pets at Home affiliates Your Design and Photobloc.
5. The discount will automatically be applied at the checkout.
6. We aim to deliver orders placed on standard delivery within 4 working days. Items delivered direct from our suppliers will take up to the time stated in the product details.