Greg
I think you should get yourself another 5 sets, make them up the same way and start flogging them on ebay......you'd make a tidy sum.
I wouldnt want to be a middle man, any money i made would be at the expensive of other
Cupra owners and thats some seriously bad karma!
As with all jobs, i think it works out a lot cheaper when you supply the garage with the parts, the bolts the discs the claipers etc etc
All the costs you take away from a garage removes their cut! thats a great way the save money, ideally you would find out how long a garage say they can build a system, then how much they charge per hour of labour (in that order!) then get a quote! but be sure your quote includes every thing you need;
One set of calipers - any type, they can be machined to fit, just dont go too big
One pair of mk2 golf braided lines,
Audi TT 312mm discs
Pair of brackets (can use alloy billet, but i prefer to over engineer!)
My set can be bought with only 500miles on them for £700, i seriously need some cash fro xmas!