Maybe start with getting hold of a copy of your car's CAR DATA, that will provide you with most if not all the options, in terms of PR codes, applied to the initial build of your car. Be warned, many after market spring suppliers only supply say 6 spring options where VW Group offer maybe 15 spring options.
Edit:- any SEAT dealership's parts department can provide a print out of that either free or at a small charge, just quote your reg number.