I'm really liking the work you've posted rob, please put some more in the art thread.
My recent work has been mainly in inks. I like to paint base colours then go over them and later reveal them by adding water and either going crazy with a brush or using a cloth/tissue paper. Sometimes I like to go over things in charcoal if I want an effect or detail. Here's a couple of examples
At school I mainly used acrylics but have never used oils. I keep meaning to get some but finding time to create art is getting scarcer now i'm at uni.