Photoshop :: Multiple Images On One Canvas.

There is a well known Photography studio chain that takes pictures in a white room and produces a multiple image canvas, which it frames and sells to you at an extortionate cost.

Is there any easy way of producing the same result with Photoshop ?

I have experimented with layers, but getting the pictures lined up in the right position has proved problematical. Ideally I'd like someone to tell me that there is a utility or plugin that allows you to create a canves,drag and drop, resize, add borders/effects and edit picture onto a grid, resulting in a professional finish.