How much space?

I am finally reaching the point of sorting out a permanent alottment space within my garden. Not quite, but nearly!

So, how much space would you allow for growing fruit and veg for one person? Bearing in mind I can utilise other spots so my raspberries and rhubarb, for example, are growing elsewhere so won't need to be accounted for. Also allowing for a lot of potatoes!

I'm just deciding where it's actually going to be so if I know roughly how much space to set aside, that will help me make the decision