If you're growing in beds, raised or otherwise you have a good choice of ways to protect your crops.

Cloches are easily moveable, but need to be well anchored. They will only be useful in the early stages of growth for most vegetables, as they are usually not very tall. You might need several, so bear that in mind.

Cold frames are handy for hardening things off in between the greenhouse and the "great outdoors", and are good to put pots or trays of seedlings in. They don't replace the need for cloches or some other protection on the beds themselves, however.

Polytunnels are generally bigger and allow you to walk inside, so I guess you could make one to cover several beds in one go. It will help in the spring and autumn particularly, and allow you to grow some crops through the winter with more chance of them surviving. The quality of the covering is important - the plastic needs to be able to withstand a lot. It could be expensive and difficult to construct yourself.

So, what would I do in your situation?

I think I might make some large hoops to go over the raised beds and then I can choose what cover to put on them - plastic to warm the soil, then netting to protect the crops, perhaps. Fleece in the winter. The tricky bit is anchoring the material so that it is secure and keeps out the weather or insects, as desired, but on this scale it's not too bad.

If I started my plants in pots, then I might rig up or buy a cold frame too. I would make it fairly hefty or put it in a sheltered spot. Wood and glass is preferable to me.

I would see how I go with the raised beds this year and think about a polytunnel next season when I have a better idea of what I'd like to achieve.

Oh how I wish I had your raised beds