I agree with HEM. You should be able to place the Motion Title on Video 2, above your video, and it should not break the video on Video 1.
To see the video through the Motion Title, go to Motion Title Adjustments, select the Background and set the background to transparent.
OMG, that was so easy! Thanks, Steve and HEM. All I had to do was change the opacity of the Background!
I dragged the slider all the way to the left and bam! - the grey background disappeared, the Motion Title animated bit stayed put on top and the video in the background played underneath.
That is exactly what I was trying to achieve. I can't believe I didn't see that for myself. Oh well!