Joiner to make external French door?

[poppet27]

We are trying to reinstate the French door usually found at the end of Victorian living rooms into the side return outside.

Our builder will knock it out & the lintel is still in place.

But I figured it would be more cost effective to get a local joiner to make a timber French door and supply the glass rather than a window company. Please tell me if I'm wrong though.

http://i66.tinypic.com/20frbk4.jpg