Do you have the Triple R Diffuser on there the now? If so and selling I may be interested..
As far as the Cupra R Diffuser + Exhaust, this site sells both: http://www.caraccessoriesplus.co.uk/product/seat-cupra-r-spoiler-rear-diffuser.html
Nice one, keep me posted if you do think about selling it. I'm based in Central Scotland also.