I am the proud owner of a Quinny Buzz but the storage will always be a bit of an issue if you just rely on the basket that hangs underneath.
Whilst I was at the Baby Show at Earls Court, I bumped into the owner of Buggy Baskets who has created a range of bags that clip onto a variety of pushchairs. They attach quite simply with four straps, are waterproof, and even have reflective lights for greater visibility at night. They can take up to 4KG and from what I saw, you surely can pack a lot away in them. I was very impressed!
The downside is that they can’t be used with 2007 models with the hood canopy on, which rules it out as a purchase for me. But kudos for coming up with a solution to a big problem.