Hi All,
Just thought I'd post an update; after much thought, I've decided to go down the JCW suspension kit path rather than some other aftermarket solution. I've contacted my local BMW/mini garage they have informed me that you are able to purchase the JCW springs as a single item, which was a surprise to me, as I was expecting to have to fork out for the other gear as well.
The tech as informed me that before he can get a price on the springs I need to supply my VIN, because apparently they need to check what equipment I have installed. I guess spring rates and other things may need to be tweaked depending on how much weight/equipment you have? I'm not really too sure.
Anyway, if there are others out there wondering if it is possible to purchase JCW springs as a separate from the suspension kit, it looks like there's some hope!