You can use this technique in tandem with the answers previously given here.
If I understand your question, there is a way you can perfectly snap multiple uv's to the same spot for perfect manipulation, which i figured out with some inspiration while trying to figure out this very same issue.
Using the 3D cursor (or in our case, the 2D cursor) we'll snap all of our desired selections to a single point. Here's my example, where you can see my similar UV's below:
Next, we'll use Blender's fancy-shmantsy cursor-snapping tools!
You can access Blender's Cursor-snapping tools using the hotkey ⇧ Shift + S or through the UV dropdown right next to the image-browser
Finally, we can get to the goodies! When we try snapping with the method presented above, (the method is Snapping > Selected to Cursor [Offset]) Each UV will be moved by its exact centerpoint, landing directly on top of the 2D Cursor! (Brilliant, right? Don't you just love inspiration?) Inspiring examples below:
Important Note: Make absolutely certain that you don't choose the default Selected to cursor option, and instead choose the Selected to Cursor (Offset) option! That Offset is your lifeblood, my young padawan! If you forget to choose the one with offset, your UV will collapse into an infinitesimally small point and cease to be recognizable as anything other than the essence and epitome of your sheer and utter failure to read a storming stack-guide. It is entirely unrecoverable, regardless of how many wanton tears you shed for it.
L, ⇧ Shift + S > 7
L while hovering over the desired UV to SELECT, and then you SPAM-SPAM-SPAM that ⇧ Shift + S > 7 combo, (pressing 7 is just a faster way of clicking that little Selected to cursor (Offset) thingy, allowing you to bypass the fiddling trouble with the mouse.