Don.
I have run some tests with the Flash, I am glad now I did. I have been using it in the wrong mode. There are three settings No1, No2 and detect. I found the detect was very fiddly to use because when the camera goes into standby I have to detect all over again. I have been using it in no 1 mode, I saw and heard that the flash was firing so thought nothing more about it. Any photo's I took where lit up by the on camera flash. Today I decided to completely cover the the on camera flash in the forward direction with my hand and just leave enough of a gap to fire the slave, all I got was black pictures, so tried the curtain sync in a different mode still no joy. Then I put it into the no2 setting. This one must be the correct setting for my camera.
I have made a temporary diffuser for the flash as you can see in the photo and put a plastic top over the on camera flash. I have taken lots of photo's all at different f stops and have now found the ideal setting for various distances.
I have included two photo's one of my hall 13ft long 200s, F5 this was done with the diffusers and one of a vase of flowers at 6ft 200s, f8. I have some I took of Mario but he won't let me use them they have also turned out very well.
Phew!!! Glad that is over. It could have been a big mistake.
Christine