The new "auto update" for v.3.2.0 is welcome, but (on a PC) it forces installation to Drive C: which is a pain as I have my previous installations on another drive.

Do I now have to migrate SD to C: or is there an option somewhere to install to the existing folder or a drive of choice?

SkyDemon's program files always get installed to your Program Files folder, in the SkyDemon subdirectory. I'm afraid there isn't an option to change that in the installer as we're trying to keep it simple.