Shouldn't matter which way you face a potting shed as it isn't for growing plants in. A greenhouse would be better facing east.

Does it really matter, it is a shed. I would have it with the door as close as possible to the house back door to shorten the run if it is raining heavily or with the nicest possible view from the window.

I would say place it in a direction you can get in and out of it easy - lol

Thanks for the answers. I am going to start my seeds, etc., off in the potting shed, so I thought it might matter which way it faces.
I shall certainly make sure, I can get into it, Triffid.....!

Canalhopper a potting shed won't have enough light for you to grow seeds in. We have a large potting shed that we can work in when the weather is bad but for starting off seeds you need a greenhouse.

Thanks for the advice, Moon_grower. I'll just carry on putting them in the conservatory then!

That will work much better...

Can you put a cold frame against the wall of your potting shed. That way you could do your potting in the shed and put the seed trays in the frame. Neither a shed, unheated greenhouse or a fram will be as warm as the conservatory.