Vertical blind for 5 metre wide window

[DonKiddick]

I want to fit a single vertical blind to a french window that is almost 5 metres wide with a drop of approximately 2 metres. I want the blind to be a single unit and bunch to the right because I need access to a door on the left. Does anyone have experience in fitting such a blind (either inside or outside the recess? Does the headrail come in one 5 metre long piece or is there a join in the middle? If so, how do you ensure smooth movement of the hangers / carriages over the join?
Thanks.

[emeritus]

If you google window blinds you will get lots of sites most of which have measuring guides and advice.

I found them really helpful for a similar situation to yours