Whilst making the most of the other deals posted (Hills Science Plan 2Kg BOGOF and the Felix 48 pouch offer), I was given an extra 10% off my basket total.
I didn't put any voucher codes in etc - it just applied it and stated:
"Save 10% when your spend £75 online (excludes Gift Vouchers)"
I couldn't find any details about this - so don't know exactly what it applies to or for how long. However, it may be worth a try if you're near the £75 mark anyway ...
EDIT: Now showing on homepage with the following info:
10% OFF orders over £75
Terms and Conditions:
1. Discount will automatically be deducted at the checkout.
2. Offer does not apply to any purchase of personalised gifts made through Pets at Home affiliates Your Design and Photobloc.
3. Offer not available in Pets at Home stores.
4. Offer does not apply to the purchase of gift vouchers.
5. Offer ends 9am on 17.07.09.