Thank you for your time Jitendra (apologies if I haven't said this yet)
I noticed he is a Windows user so will not be effected by OSX inability to remove Quicktime.
This thread has a similar problem where the OP came up with this solution
This has been doing my head in but I have solved it!!!
My trick was to bypass Lightroom - go into the movie file and open it WITH Lightroom (rather than the default Quicktime): The movie then appears in Lightroom and all I had to do was click the Import button and the movie got imported!!! Seeemplz. I have done it for about 10 movie files so far and it works every time. I am very happy.
However that solution does not work for me either
I notice that other users do seem to be affected though?