"Mr X"wrote
My garden is 7 metres by 2 metres, its the 7 metre length that I want to
hedge. I dont want my hedge thicker than 60cm if possible. I did think of
planting sunflowers as there is plenty of light but they are annuals and
therefore harder work

At 2 metres wide I'd use a fence, or trellis for plants to grow up, to save
space.
Talking of climbing plants...over to you Charlie. :-)

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Regards
Bob Hobden