Thanks for doing the measurement - I've got a 184 SC (same colour as yours Woody) and bilstein site was coming up with both 55 and 50mm front struts. The rears are definitely independent rear suspension. Was tending to Bilstein B6 as I'd be planning to keep the FR springs to keep the same height.
I came from a Mk7 Golf Gti and find the ride in the golf was much better, would love to know what SEAT changed to make it so much crashier, especially at the rear.
Been looking at Koni's, Bilstein etc but no decision so far, want an improvement, but not rock hard or scraping the ground (well past the wrong side of 40 lol) so would be keen to find out what you get and if what you get improves things.
Might be later in the year, spent a fortune this year, 40k service, DSG oil & filter, cambelt & water pump - ouch.
Cheers,
Neil.