Welcome to ATP,
I don't know which vegetables, if any, are native to your area. I did some quick research and find most of the common vegetable origins. Don't know how accurate this information is but it may help you to rule out some plants:
I found another site (have no idea if it is accurate) which lists edibles supposedly native to Northern Europe:
Apple, Black Currant, Damson plum, Pears, Raspberry; and vegetables: Angelica, Mustard, Parsnips, Radish, Rapeseed, Turnips.
Fruit trees and hedgerows...Vaccinium myrtillus/European Blueberry, Sambucus nigra/Elderberry; maybe Cherries, Sorbus aucuparia/Rowan, Prunus spinosa/Blackthorn/Sloe , Hawthorn, Holly - some bear fruit for wildlife only and NOT for human consumption.
There have been so many different cultures bringing plants to the UK over the centuries that it may be difficult to determine which are true native plants. Good luck with your project.