Sadly the second Gen R56 is full of issues way more imho that any of my first gens at an equivalent mileage as i discovered to my horror especially the petrol models,valve issues,timing chains,carbon problems,engine electrical issues,valvetronic problems,all you need do is look in the forums, the diesel engine is great we have a cooper d and with nearly twice the mileage of our petrol cooper haven't had a single issue in over a year,the diesel engines were a ford euro based engine whilst the petrols had the crappy PSA Peugeot/citroen engine not worthy of the Mini/Bmw name imo.......my petrol cooper is 07 and from reading the forums a lot of the issues are starting to surface now at 50-90k many whilst still under warranty at like 20k .....if it were me i would'nt even dream of buying another petrol R56 without a main dealer warranty even if it was £1000s cheaper......if something goes wrong £1000 is pocket change most of the time to diagnose and repair the fault.........just my tuppence worth man from what i've read and experienced first hand with my own cooper........if you do decide to buy outside without dealer warranty i would insist on a full service history so at least if any of the recall issues go wrong the dealer MAY still cover you......
Things to check
no eml/or dash lights on inc airbag
rumbling or knocking from the rear over bumps
Clicking or knocking from the from when taking off in first
no smoke on startup and while driving
The car should Idle smoothly with no dips or peaks
No lag when under acceleration all the way through the rev range... yes to the red line...
Check for any oil around the engine joints ie head/rockercover
Car should start first time hot or cold
Check for smooth engagement of the clutch biteing point usually around mid pedal..... too high is not good
Check for sticky gearchanges or grinding or non centering gear stick when returning to neutral
Test drive the car and drive it HARD for at least 45 mins or more on all road conditions
Thats just what i would check if i were buying obvious most of it.... but we can all get bitten from time to time with cars
Hope i haven't scared you off
still a cracking wee car if you manage to get a good un i absolutely love our cooper D puts a smile on my face every time i drive it....