And that was the madness with mine. The owner had had the big 4 year service done including the lambda's etc 2 months before he decided to part-ex, he'd even ordered two new front mats that hadn't even arrived when I bought the car off him! I drove the car straight from his house to my detailer, picked it two days later in showroom condition, with 6 months of the Maser warranty intact to cover niggles!
When it works that well you are fine, if the vendor has extended the warranty for year's 4 and 5 and you buy it in that period then they make great private buys. Indeed he had to get the full 4 year service odne as it would have invalidated his extended warranty not to have done the O2 sensors and fuel cannister. Mind very few people buy/sell £40-60k cars for cash with the finance situation often getting in the way.