Oh, I'd put the doors in line with your inside door. That way you can have space either side of the door for pram, umbrellas, shoes, etc. we had our porch door rehung so that it opened out the way as we were having to walk around the open door iykwim.
Our porch is smaller and there are quarry tiles on the floor and then a huge piece of coir doormat that I had cut to size. The doormat goes from the exterior porch door to the interior front door.
It's fab and has really worked well at trapping the dirt, leaves etc. I just Hoover it. I think I did read somewhere that the best way to clean coir matting is to hose it down outside, though not tried it yet. You tend to get a darker sort of stain in the middle of it.
As part of our extension we are adding a 2.5m x 1.2m porch and I'm starting to wonder what to put on the floor.
I'm assuming the laminate we're putting through most of downstairs will be trashed quite quickly so was thinking of slate effect tiles. But then I wondered if it was worth looking for coir matting to cover the whole floor so the whole floor is a doormat. Would it be OK just to hoover this occasionally or would I be better to get one that I can pick up and shake out?