I believed that in the past the Xcellence had them as standard, however nowadays, I believe only Xcelence Lux has them (could someone with Xcellence Lux confirm?). Washers are legal requirement if single source of light exceeds 2k Lumens. My
Ibiza Bi-Xenon had them, and my Leon SE Tech Pack MK3 1st Gen (2013 model) LED headlights had them, even though I had no winter pack. Perhaps when Seat first released the LEDs, they fitted them 'just in case.' late 2014 Leon models with LED headlights did not have washers anymore unless winter pack. You would notice, that for instance, all Audi A3 LED (single source) headlights have washers, and even the Mercs E class with dual LEDs (not single source) do not have these washers. However the Golf GTI/GTD with
lower 25watt Bi-xenon or current dual LED headlights did not require them. The total light output from the FL Leon LEDs may exceed 2k Lumens, but not as a single source. Washers are especially useful (yes not in UK) in snowy winters as they can wash away the snow or ice that cannot be melted away from the head of the lights.
From experience from the driving seat, LED headlights (from Mercs, Prius, Seat, BMWs) are not as glaring and jittery as the Bi-Xenons of approaching cars. However, I'm not sure why the Mini and Qashqai's LEDs are glarring and jittery....that said, I never had issues with my headlight washers except that they empty the screenwash far quicker, plus they are especially useful if pedestrians get too close to the front of my car at night
...
Anyhow, now that I have a Volvo V40 with LED headlights (damn they are bright) no headlight washers, as it's a 2 LED per headlight source, everytime I put fuel in, I just spray the headlights manually with my bottle, and wipe clean with cloth...tada, done!