It sounds like a fruit cage - Have you thought about using it to grow fruit bushes and building a separate polytunnel? Or just adding a hoop house to a raised bed?
My concern would be if it’s box shaped, then it might appear sturdy, but when you add large sheets to the sides, the wind becomes a big factor. Tunnels are far more resilient and also shed rain - I don’t think snow should be much of an issue in southern UK.