New plot, nothing growing - need your help

Gave up our lottie earlier this year as we'd bought a cottage with a huge piece of ground. The ground had lain idle for last 10 years or so partly covered in plastic. Prior to that it had been used as a veg garden and, decades previously as a successful Market Garden.

I cleared the ground completely, rotovated, then set out beds, fruit cage, planted new fruit trees and bushes, moved my strawbs from the lottie, marked out paths and put up a new polytunnel. Almost everything outside has failed to either grow or germinate but the polytunnel is going great guns (everything in PT growning in bed/borders in the same soil as outside). I've listed how things have gone below - can anyone suggest what's gone wrong? Almost everything outside has failed - is it just the horrendous weather/lack of light or something else? Please help

Potatoes
Healthy buy tiny crop, very small shaws (earlies)

Cauli, Cabbage, PSB, Sprouts, Brocolli, Turnips
Direct sowings in April and May failed to germinate then young plants brought on in PT then planted out failed to take root and have been on strike for the last 6 weeks.

Broad Beans & Carrots
Sown direct - growing slowly but looking healthy

Onions, Garlic & Leeks
Still very small but healthy (though something had been nibbling the onion/garlic leaves)

Strawberries
Utter Disaster - loads of flowers but berries remain tiny, green and refuse I swell or colour

Fruit Bushes (White/Red/Black Currant and Gooseberries)
A little yellow looking - only a few berries

Beetroot
Poor germination then failed to grow

Rhubarb
Doing well

Pumpkins & Courgettes
Growing, but slow

Peas Beans
Direct sowing failed, planted out young plants brought on in PT and they are coming on very slowly

Lettuce
Direct sowing in May still tiny, not even large enough to thin out