Bubbles ... I feel you are in need of a sensible answer .... wheat, barley, oil seed rape and sugar beet are the main ones, with more regionalised crops of maize, linseed, borage, plus the usual veg crops.. spuds, turnips, parsnips, carrots, etc
According to my mate in the village (who is a farmer) the largest crop grown in Northants is grass! Although used for grazing, it still needs to be managed and 'grown'. Next ones are wheat, rape and barley, but we have noticed a lot of fields with that bamboo looking bio fuel in it (sorry, can't remember the proper name).