If you're not doing a lot of shopping regularly, then the under-tonneau tray is very useful for holding the bits and pieces, like User Guide, spare footware and socks, first aid kit, tissues, hi-vis jacket etc.
I also employ a Tesco Wine Carrier for the liquids (window washer, rain-ex, bug cleaner), fire extinguisher, window squeegee, window wipes, kitchen towel etc., stashed behind the passenger seat.
Adding a bag holder (ASDA, about 3 quid, has two large hooks, will hold large shoulder or handbags, and backpacks) for the headrest post of the passenger seat avoids the bleeping when the empty passenger seat thinks it's loaded.