I have a Toyota Yaris which is extremely similar to the C2 (my parents have a C2). I have also bought the silvercross 3d from Mothercare in JetSport http://www.mothercare.com/gp/product/B000UPEMTA/ref=ts_dp_1/026-1361750-0527630?ie=UTF8&mcb=core
I've checked it and it fits in my boot brilliantly!! Make sure you take your car with you to try it out before buying! Mothercare staff are fantastic and allow you to try it first!
Also, we opted for a base and car seat which is sooooooo much easier if you have a 3 door car like me!! Once the base is in you just 'click and clunk' the car seat in place without having to faff about with the seatbelt all the time.
Good luck x