Crossfire plugs are generally about £7 each, so don't let your mechanic charge you a tenner!

There was a guy on Ebay a few weeks back who was selling a set of 16 for a CL55AMG for £32 delivered! They are the same plugs as the XF and I had a set off him, you just end up with 4 left over! There's a thread about it in the UK section of the forum.

Some of the plugs are fairly tricky to replace, so £100 for labour is about right from a mechanic.

Regards, Andy.