Thanks for those replies. I think Richard is right about the variable frame rate being the problem. I found the same problem on a few other phone clips that I tested But was able to use the editor on the mpeg 2 clips and some mp3 music files.
I tried several things last night as I had to get this completed today.
First I tried a free converter from NCH supposedly free for home use. After going through all the upload and conversion I found that the only format allowed without paying £49 for the software was AVI. This worked but it must have been AVI type one because I then couldn't load it into studio.
Another bit of free software ran for five minutes and then said it was too long for the free version!. I couldn't find anything that would allow me to convert to mpeg2.
Eventually in desperation I loaded the clips one at a time into Windows Movie Maker and was able to edit and save as HD mp4 files that I could then insert into studio.
Thanks again both of you who replied I shall certainly look for that software for future use
Regards
Quez