Hi I reset the graphics on Homeworld Emergence to default open GL and a higher resolution and this worked fine the first time - much better. Reload the game and it's off centre with the menus all at the bottom right of the screen. I can't actually access the part of the menu to save graphics changes so I can't reset them - because they're off the screen... Any thoughts please?

What kind of GPU do you have? AMD or nVidia? If you are an nVidia user, you need to keep the nVidia Control Panel open, with GPU scaling and "override the scaling option for games and programs" checked. Running the game as admin will help too.

Have you tried the fix described here :
https://www.gog.com/forum/homeworld_remastered_collection/classic_versions_widescreen/post16
?

Same issue, I can get the game up and running but half of the screen is only showing up. Can't play the game like this can we have some help please?

This could be caused by scaling in screen options. Minecraft can do the same thing you are describing when I play at a 4K resolution.

Try this: Right click on desktop, then display settings.
choose "Display" in the left panel. Right panel go down to "Scale and layout".
If "Change the size of text, apps, and other items" is anything other than 100%, set it back to 100%.

For my normal 4K configuration I have that set to 150% so my icons and other interfaces are big enough to read.
But for older games, they just don't handle 4K well and need to be set to 100% to display correctly.

Once you are done playing, set your interface back to what it was.

Be sure and right-click the executable short cut you use to run the game (a round icon entitled, Launch Homeworld Remastered Collection, found in the Homeworld game install directory), select properties, select the compatibility tab, and at the bottom of the tab you'll see the Change High DPI button. Press it, and again at the bottom of the new page, look at High DPI scaling Override, scaling performed by--click the menu and select "Application'--click OK to close the page, then click OK again to close out the shortcut properties tabs and go back to the desktop. Then left-click the game shortcut you just set the properties for twice and run the game--you should be squared away!