I am almost certain that the mech fitted the right plugs because he commented on them being different to any he's seen before anyway I'll get a new set and fit them. The service included new filter,
(I used Castrol High Mileage 15w 40),air filter. Running lumpy before all this, however when I got a new keycard programmed the dealer noticed the problem and (for free!!!) did a quick diagnostic which came up as "Misfire cylinder 1" but it runs ok at 2000 plus revs, gives 30 mpg average and pulls ok up hills (there's quite a few round here) I am still waiting for a full diagnostic but everybody's busy, so when its done I'll let you know. Many thanks for your advice
PS just for the record what is the correct plug number/part number?