I used to get Denso irridum sparkplugs from rockauto, all 8 for around £34 including delivery.
But this year I thought I'd get all the parts from Lexus dealers here, 6 litres of oil, oil filter, washer, air filter, cabin filter, 8 irridum sparkplugs, all for £93, took it to my local garage, watched them do the service and was charged £30