Yep - you are right, opening it in Quicktime does report it as being ProRes LT.
What threw me was that when trying to use the clip in Motion 5, it was saying that Motion 5 does not support that codec. It had been working fine 10 minutes before!
However, the clip now WORKS again in Motion 5, so it was actually Motion 5 having a problem, which is now sorted and gone away - I can carry on with work after spending a few hours trying to solve a problem that was just a glitch!!!!
Thanks for replying though - appreciate it!