Hi Jacqui,
I’ll partially answer your question in that Charles usually recommends manure about 18 months old, though as long as it is not ‘fresh’ when you use it (stack it and let it mature)and not too wood chippy or strawy (robs nitrogen and harbours slugs) you could be ok.
I would concentrate on veg you like! But other than that things that taste far better fresh than bought, like peas, or offer large cropping for little space like climbing beans. You should be ok with carrots/beetroot/lettuce/spinach etc because they’re fast growing and don’t take up much space. Even if you grow veg that need more room like brassicas you can always intercrop with something quicker growing like lettuce before they need the space. Remember too that most veg only take up a half season so you can follow one with another.
The plastic boxes you mention are used mushroom boxes and are often freely available from greengrocers, veg wholesalers and probably supermarkets.
Charles has a large cedar greenhouse and polytunnel. He doesn’t heat either.(Except for a hot-bed in the corner of his greenhouse for propagating seedlings). I can’t remember whether his greenhouse had bubble wrap, but probably did.
Hope that answers some of your questions
Jan
