Suzy, I saw on our local allotments that people drap their netting over bamboo canes with small drinks bottle's over the end. The drinks bottles not only stop you poking your eyes out but also provide a surface area for the netting to sit on (ie not 'fall' over the bamboo via the holes in the netting - I'm explaining this badly aren't I?
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It's cheap because you already have the netting (I think?) so only need to buy some bamboo (not expensive) and the bottles are a waste product andway so you'll be reusing somehting that would otherwise be recycled..
Then at the bottom, could you hold the netting down (and stop birds getting in underneather ) but pinning down with bricks or metal U pins made out of metal coat hangers?
Is this the kind of thing you were after to hold a net in place? You can make it as tall or shot as needed by adjusting the length of bamboo you use