Hi there hope someone can help, I have 3000 x 3000 px square and 4 images that have to be place in the center of the corners, so they hanging over the edge of the square but dead centred so when duplicated makes a seamless tile, please see the image attached for a better idea. Many thanks.

If the object is symmetrical (in both directions), you could snap the center (or rotation center) of the object, to the corners of the rectangle.  http://tavmjong.free.fr/INKSCAPE/MANUAL/html/Snapping.html

If the object really is a circle, it will need to be at least temporarily filled before you can snap to the rotation center.  Any other object can snap without a fill, but for some reason, circles need to be filled, for the center to snap.

If the object is not symmetrical, it gets trickier.

Edit

If you can say, I'm curious what you're making the seamless pattern for.  That's a pretty large unit (3000 px)

Than you will try that, the image is a cartoon dog, so not symmetrical. Does that make a difference.

I am a designer, just staring out, it's for wallpaper, fabric, wrapping paper. 

Here is the image that I need in the corners

Here is the image that I need in the corners

Oh, it seems I was wrong about that!  You image is symmetrical.  But it looks like it should work even with asymmetrical objects.

I still haven't a. Luke how to do it, lol.

I still haven't a. Luke how to do it, lol.

Scrub that worked it out omg, your a life saver and a saver of hair, can't thank you enough.

Scrub that worked it out omg, your a life saver and a saver of hair, can't thank you enough.

Scrub that worked it out omg, your a life saver and a saver of hair, can't thank you enough.

You're welcome  🙂