I don't think the currants would provide much of a wind break for the fruit trees (they'd never get taller than 2m max, I think) - I think it works the other way round there. But most apples and pears should be OK with a reasonable amount of wind, shouldn't they? I've been careful to shelter the more sensitive fruits - peach, apricots, almond, persimmon, cherries - but our apples and pears are having to cope with whatever the weather throws at them. Having said that, now we're planting windbreaks, we'll put one that'll help keep the North winds off the orchard too.
But it's a great idea to go for bigger edibles. How about nut trees? You might not get many once the squirrels have had a go and they're not very fast growing but they get to a decent size. Or, like you say, the standard edible hedging of blackthorn, roses, hawthorn, elder, rowan etc.
I'm not sure about the spacing for trees and currants. I guess it depends on the size of your fruit trees and their root stock. Ours are on MM106 and about 7m apart so I think they'd be fine to have a couple of rows between them. You could send Brogdale (national fruit tree collection - they also do currants and gooseberries) a message. They don't coplant but it's the sort of thing they'd know!