You have every sympathy from everyone on here; of that I am certain Hevski.
But every year brings different challenges and I am sure if you look again in a few weeks you'll feel a lot more positive about your plot. We only missed the frost by one degree here. Again sympathies there.
I've had years where I feel the same in my back garden. I have four 3.5m by 4m plots set to different things, a greenhouse that nearly fills one, one for loganberry, apple, and blueberries, one for gooseberries, asparagus, comfrey and this year potatoes and beetroot. The last one this year has sweetcorn, borlotti, garlic and various squashes (to try and find out which ones we like best and which grow best).
I write this to explain the background as to what went wrong last year. The sweetcorn got hammered by high winds in July (we're three miles from the coast in Essex) - no crop. I imagine Cambridgeshire has a high winds as well. Last year I planted 48 borlotti seeds my way; tried and tested over twenty years... dig a small hole fill with water, drop the seed in, back-fill with soil and water again leaving a small dip to concentrate the water on the bean. Never failed. Until last year when FOUR came up. FOUR. This year after reading on this site, I chitted them and got 19 out of 20. Pretty good. Better than four out of forty-eight.
Last year's lettuce in the greenhouse were so eaten by blackfly they went from the greenhouse to the compost bin, no stopping, no collecting £200, do not pass GO. The female blackbird learnt a new trick... flick a loganberry from the twig and then fly down to eat the fruit off of the path. 40% of the crop eaten by one family of blackbirds (I have the nets ready this year). The dwarf beans failed miserably. Dwarf as in crop size I thought. We've had more already this year from just four plants. We had sixteen last year.
But, but, but, hang-on, the carrots, well; dry hard clay soil in the driest part of the UK and we had tons of them in late October. I was amazed. We froze a wheelbarrow load (honestly) from a 4m by 0.5m broadcast strip, in the spare freezer and only eat the last of them last weekend. The garlic went nuts too. The asparagus thrived, the six tomato plants gave more than enough crop, okay the cucumber was useless too. But this year everything looks good.
So here's the thing, don't give up. You could still sow beetroot, some bean varieties, peas, plant late potatoes. You may find something heavily discounted at a local nursery. We found a fantastic one local to us that is run by a married couple on their own, delightful and full of knowledge. Never considered going there until the failure four years ago. Now won't go anywhere else. You might find a courgette that is pot-bound, a struggling leggy tomato, or two, or three, that needs love and attention, and decent soil around its roots, a pumpkin or or squash plant. Or that other thing, you know, the one you didn't know about and don't know what it tastes like, that one.
Or, as I did four years ago when we had over 100 days without rain and a hosepipe ban, I redesigned the beds to plant the fruit bushes, asparagus and apple tree so that I only needed to water very little. I added two more water butts to the collection (nine now). Oh, I even planted gladioli in a raised bed by the greenhouse to satisfy my wife, and a lonely carnation that she seems oddly attached to. I didn't argue, I just planted them. I made a new improved compost bin from second-hand decking boards. Made a fire-pit type thing using a drum from a knackered washing machine, which I put on concrete blocks to make life easier. Wonderful.
Chin up Hevski. There's always next year.
