www.sparkplugs.co.uk

yup, I ordered mine from them... although they send it to wrong country (Croatia instead of Serbia as i wrote in order form???). Package was stuck for 2 weeks in Croatian post-custom office an finally I received it after 3 weeks... but still 2x cheaper than local dealers...
No hard feelings, they sounded nice, since Serbia wasn't even on list of countries, they added us 15min after i wrote them complaining mail :)

Apart from life expectancy do they really change the bike's performance in any way? Fuel consumption, acceleration or top speed?

Cheers!

to be honest i didn't notice anything different :D

No they don't make any difference in performance at all, they only last longer.

Thanks! Will consider it when the old one is dead. Still plenty to go.