Hi Caz and welcome to GoY, for veg. I'd go with a large polytunnel. What are you planning on growing in it?

Unless you live in a very cold part of the UK, you do not need either, except for things like Tomatoes, Chillis, Peppers etc. IE the tender stuff. We grow all our other veg outside with only a covering of netting and/or shade material to keep away the pigeons and cabbage whites. And this is certainly not a warm part of the UK.

Friend's of ours grow a lot of different veg. in their polytunnel to extend the season. It enables you to start things growing in autumn and keep them going through the winter, plant your early potatoes sooner, ditto peas and beans Peter even grows onions and the like in the tunnel... they are completely self sufficient in veg. soft fruit and top fruit. Owdb. I'd love to have a polytunnel for veg. and we are not in a particularly cold part of the country, the tunnel would extend the range and variety of what we could grow.

There is a difference betwixt 'need' and 'desire'. We have a polytunnel We are also completely self sufficient in veg and fruit (except for the bananas and lemons and peaches and grapes). Our polytunnel extends the seasons for us, but it is not 'necessary'. We grow most of our veg outside and we are definitely in a cold area.

For us a polytunnel would mean being able to grow courgettes, cucumbers, bell peppers, better bean crops... so many veg. we can't grow outside or in the wee greenhouse where we grow our tomatoes. The basic diet up here in winter without a freezer or access to a green grocers is incredibly limited. Potatoes, kale, swedes, cabbage, Brussels sprouts, carrots, leeks and onions. No wonder they used to cook nettles and dandelion leaves in spring when they came through - anything for something fresh and green.

Having said that, I would swap our 30 'by 15' poly tunnel for a glasshouse of the same size any time! :)