I am off on holiday to Dubai very soon, should I use a slightler higher ISO whilst I am there on account of the brilliant sunshine leaving the camera on Auto, or should i leave the ISO at 50 and shoot manually??
Yes..as Matt has said the lower the iso the less noise you will have in your pictures. As you are going to Dubai which would suggest that the lighting will be bright and sunny this should not stop you taking any pictures ar reasonable shutter speeds.
Basically the only times you should increase the ISO is when the camera sets the shutter speed to below what you require due to low light, or if you are trying to create a noisy photography on purpose.