PUZZLED - OPC service charges

[xTVR]

Fairly new to Porsche ownership, so not used to OPC modus operandi. Puzzle is this, 996 c2 (3.6itr) is in today for 24k service. Just got phone call from lovely Yorkshire lass on reception to ask if I want new spark plugs at extra £160 as car is now 4 years old. Arent plugs a standard part of a 24K mile service anyway? Never had to pay extra before. Is this normal?
Also, they are keeping the car an extra day to replace the RMS AGAIN (last time when I got the car 7k miles ago). Should I be worried?
Sounds a bit like an agony aunt thing does this but I'm sure someone out there can enlighten me. Answers on a post card please!
Thanks guys.