Cyberlink Power Director 7
By this time I was getting very fed up. I installed the trial version of this and immediately thought that the interface looked very nice and straight forward. I then imported all of my son's video clips in the media library and there they were complete with thumbnails

(so far so good). I then plucked up courage and dragged one onto the timeline and there it sat happily with no crash. I clicked on play and it played with no crashes, (I cannot tell you how relieved I was at this point to have found something which enabled the clips to be used straight from the camcorder with no conversion and that actually looked like it was going to work without constantly crashing).
We have now had a good play with this editing package and it appears simple to use, very intuitive and robust, (flicking between it, the internet, desktop and file manage does not appear to phase it at all). We have uploaded videos to YouTube using the built in uploader and also saved higher resolution / quality M2TS clips to file and then uploaded them in the usual way and I must say that so far this package looks to be ideal for us.
While the Samsung MX20 camcorder that my son chose is not a very high resolution, I must say that the results combined with this editing package are very good and I can see fun times ahead
Thanks again for all of your help guys in getting us to this point
P.S. The only slight bug we have encountered with the Samsung MX20 camcorder , (and this has been previously reported on the web), is that when shooting in 16:9, the clips are not given a 16:9 flag and therefore when imported into video editing software they play as 4:3 which obviously results in the images appearing tall and thin. However in Cyberlink Power Director 7 this is easily corrected by right clicking on the properties of a clip and manually setting it as 16:9, (there is even an option to apply this setting to all clips on the timeline - great stuff indeed)