To the OP:
- The 2010 model is the last year before the facelift model was introduced. The facelift is improved in several ways, so make sure that there's a significant price gap between this car and a 2011 (fscelift) car - otherwise you are paying too much...
- This car will have the M271 engine that is known for premature timing chain failure, which can wreck the engine. Rough idle at startup from cold (e.g. after being parked overnight) is a dead giveaway. You have five options here: (a) only buy a car that already had the timing gear replaced, or (b) have the car inspected by a specialist before buying, or (c) buy the car and set aside some money to have the timing gear replaced preemptively, or (d) buy a C350 with the V6 petrol engine, or (e) buy a Diesel.
The problem with (d) is that the V6 petrol is both rare and expensive. The problems with (e) are that 2010 Diesel cars are not compliant with ULEZ (which currently only affects London) and that it has a DPF which makes it unsuitable for short journeys - but if you don't drive in London and do 10-15k miles annually then the Diesel will be fine.
But if you are keen on a C-Class with a small petrol engine, then don't ignore the timing chain issue, and opt for (a), (b), or (c).
- The C-Class can suffer from knocks from the front suspension at parking speeds. When test-driving the car, make sure you turn the steering wheel lock-to-lock at parking speeds and listen for a metallic knock from the front suspension.
- The variant in the ad is the Sport model, that has the additional body spolier kit, lowered and stiffened sport suspension, and 17" wheels. All of which are aesthetically pleaseing, but make for a harsh ride. The Classic and Executive variants (as opposed to the Sport) will not have the spoilers and will have a higher soft-sprung suspension with smaller 16" wheels, so it won't look as nice, but the ride will be more comfortable. There are also differences in the internal trim and seats, but these are less important.
- The Artico is fine and generally durable and wears well, although some owners reported split seams, so check that. Real leather is quire rare on the C-Class anyway, the vast majority were sold with Artico.
- The manual transmission in the C-Class is not the sleekest of boxes, and not to everyone's taste, but it's reliable and dependable so it's just a question of whether you are OK with it. However, given that it's generally considered undesirable, it will make the car more difficult to sell on, so only buy a manual if you are paying for it significantly less than for an automatic.
- Some cars have the optional COMAND NTG4 satnav system, with the motorised screen that pops-out of the dash - these tend to fail with the screen getting stuck half way up. So if the car has the motorised pop-up satnav screen, make sure it goes smoothly all the way on and out.
- Bluetooth telephony was an option on the pre-facelift, so if this is important to you, then either choose a car that has the Bluetooth telephony option, or budget to install an aftermarket Bluetooth kit (e.g. Parrot).
Hope this helps.