I'm not sure what happened but I get a runtime error with missing gameuxinstallhelper.dll when I try uninstalling the game.

But after the big shelf update with all the game bundles being split into individual games I can't download the same pack to reinstall it to uninstall it

Couldn't you copy the missing file over from another (GOG) installer? Or use an uninstall tool like Revo Uninstaller, perhaps?

I don't think (sadly) there is a way to re-download old installers.

I don't know what file is missing but installing the games individually didn't work

You mentioned the reported missing GameuxInstallHelper.dll, which is normally found in the directory where you installed the game. If this file somehow got removed or corrupted, you might try copy and pasting it from another source? (E.g. another GOG game you currently have installed.) Have you moved or modified the game folder(s) after installation?

Or perhaps it's a rights issue in Windows, try right-clicking the uninstall shortcut and selecting "run as administrator".

You can also usually remove software from the control panel, have you tried that yet?

Uninstalling from the remove a program menu doesn't work either
I'll try and see if I have it backed up somewhere, thanks for helping out =)