Bottom half (most overgrown and scary )
Cut vegetation (strimmer or scythe ), dig over fairly well, pile on manure (this will be the manure holding area), cover majority with weed fabric, plant through courgettes, pumpkins and squashes.
Nothing wrong with spreading manure, but it would be faster (and possibly more beneficial to the initial Squash crop) to prepare planting holes - decent sized holes, loads of manure etc in each, pop a stick in so you know where they are
cover with weed fabric and plant through (where the sticks are, natch!)
If you are going to grow Spuds consider growing only First / Second early, or giving them more priority in your mind at least! compared to Main Crop. Spuds are pretty good at helping clear the ground, but they may not store well, and Main crop will be in the ground longer and more susceptible to Blight, so as a newbie you might want to defer them until next year. I love Pink Fire Apple though (which are same growing-period as main crop)
You COULD (not quite sure if this is a good idea!) prepare trench, manure in the bottom, replace soil, earth up a little, then cover with weed fabric and plant the spuds deeply through it. Only problem is that they will have a long way to grow before they find daylight (although that is probably what farmers do in-the-field now I come to think of it). The weed fabric will help suppress the Couch Grass, but you'll need to deal with any that finds its way through the planting holes.
First year = Only grow what you like - less disappointment then, compared to putting loads of time into a crop that then fails, and you didn't like it anyway!
Secondly, grow what is good value (high yield + high price). Main Crop spuds are cheap to buy, and hard to store well. Whereas Runner Beans cost-a-plenty in the shops.
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Build some sort of netted structure to keep birds and butterflies out"
Easiest / cheapest is probably scaffolders debris netting over hoops made from blue-or-black water pipe (some pictures on my blog showing a 9-year-old at work!)