Billy
TBH mate, unless you are going to be doing track work, I'd probably avoid COs. They are pretty harsh on the ride side of things, but of course the handling is good. That said. those springs that you have along with one or two other little bits like droplinks and an ALK with fast-road geometry settings, will improve the handling of the car out of sight from the standard set up. This will be more than adequate for road-use and even works well on the track. Don't worry about your struts... I know a guy that has a full set of them lying in his garage with about 20k on them - LOL!
Perhaps the £300 would be better spent on that. Hypertech, IIRC do free fitting on the ALK and the Droppies - as they do with all Whiteline goodies. Just check that first of course.