I have a 1968 +2 which I bought in boxes. This may sound very basic, but how does the handbrake mechanism fit under the dash?

Pictures tell the story. There are variations on this layout so it depends on the bits supplied in the boxes! There are also two types of handbrake lever - Mine (pictured that uses a button to allow the lever to move in and out, and another type which rotates to achieve the same action. Note the piles of washers to space the lever, and also a broken weld along one side that allows the whole assembly to move (I must do something about that..).

Jeremy