Wow! Thanks for the quick reply…
originally the line above the clip in the timeline was green and rendering didn’t appear to make any difference.
The lines above the clips now are red and turn a dull blue after rendering. (again, doesn’t seem to alter the image).
I apologise, I have tried so many different things today that I can’t remember what action caused the line to start being red instead of green. I think it could have been changing sequence compressor settings (now on HDV1080i50)