Hey Kieran,
I think you will only be able to find 30-35mm lowering springs. I haven't come across any 40mm, have you seen some?
Either that or you can buy 60-80mm lowering springs from this site:
http://www.humphrisoxford.co.uk/upload/files/2015_09_09_Micra_Rally_Parts_Retail_Price.pdf
However I believe you would need shortened shock absorbers to go with those springs , as anything below -35mm ideally requires the shorter shocks.
You could get a set of coilovers from brightsparkracing.co.uk for £300 and an adjustable panhard rod for £55 which you will need.
Sorry I couldn't provide you with any photos!