I have constructed a temporary fruit cage using my "Build-a-Ball" kit, some aluminium rods and a net. With this combination it is easy and quick to build a suitable structure, like this:
I have a set of 12 balls, and a selection of different lengths of aluminium rod. You just push the rods into the ball, which is made of rubber, and it grips the rod firmly.
Once the cage was assembled, I put the Strawberry crates inside, draped the net over the top and weighted the edges down with a few bricks. Et voila - a perfectly acceptable fruit cage assembled in a few minutes! Incidentally, the net has a one-inch mesh diameter, so it will keep birds out but let bees in.
I'm hoping that the Strawberry fruits will ripen and be finished before the Blueberries come on-stream, because I don't have enough stuff to make another cage. If the two coincide I will have to knock-up something a bit less "professional". One way or another, the Blueberries must also be protected, because if there is something that Blackbirds like more than Strawberries, it's Blueberries! [Though, come to think of it, they are pretty fond of Redcurrants too.]