Downpipe in wrong spot- whose responsibility?

Hi,

Not a massive drama to fix ( I think), but on my house plans the downpipe is say right side of the corner of the gutters next to the sliding door.

My drainage plumber put the storm water pipe on the left of the gutter, along an empty wall.

Now, the guttering people installed the downpipe opening as per the plan, but obviously not in line with the storm water pipe.

So either I move the downpipe opening or leave it where it is and dig and connect the stormwater.

I would prefer to move it, because where it is, it's visible as I plan to have decking there (and I will have to cut the timber out for the downpipe).

It's not hard to move it, and then block off the opening, but my drainer said who ever laid the pipe first should have priority?

If this is correct, can I ask the gutter people to come back and fix it?