Finally (for now) I had it lowered. I went to AST suspension and had a set of their lowering springs fitted. I went with a 25mm drop as it is my daily driver and I live in speed bump central so decided against the 35mm. The 35mm also have a greater need for various alignment products to be fitted too. Decided to go with the springs from AST as they are the closest to stock rate and I didn't want to make the ride much firmer than it already was. They are also pretty much the only offering which have different spring rates for the '86 and BRZ.
Picture below just after fitting so I would expect them to settle a little more over the coming weeks:-
Again, please excuse the state of the car!