[i]So, I'm assuming it is reading the info from the tab 'theme options'. You say the two aren't related so no idea how it's now working

[/i]
I didn't say they are not related (ok, I said "gallery options" instead of "theme option", I admit...:-)). The image size of the options is taken for the slideshow image if you don't set a specific one in `printSlideshowLink()` http://www.zenphoto.org/documentation/zenphoto/_plugins---slideshow.php.html
[i]Would like now to know about speed. It goes REALLY fast and not obvious to click the image for controls which don't always show up (?? slow).[/i]
Again, you can set that on the slideshop.php theme page. See http://www.zenphoto.org/documentation/zenphoto/_plugins---slideshow.php.html for the details.
[i](And, it would be great to adjust layout with CSS......)[/i]
I repeat my above answer: Take a look at plugins/slideshow.php and the function `printSlideShowCSS($size)`.