Getting the serpentine belt replaced, should I ask for tensioner and pulley replaced as the R55 JCW is 10 yrs old with only 55K miles on it?
Anything else the mechanic should work on at the same time?

Thank you!

 

Accessory drive belt service… Tensioner doesn’t always need replacement, but good to have done if the funds are there for it. By “pulley”, are you referring to the crank pully? If so, not needed. Might want to consider the water pump pulley and friction wheel.