[DaveNP]

I can recall my father buying a new car which had to be driven gently for the first 500 miles of 'Running In', it then had a service to replace the running in oil which was a different spec to the regular stuff. Modern cars don't need that as they are presumably better engineered and have better oil so can perform straight out of the factory. Given your later info that they rely on sensors to indicate when a service is required and many therefore don't get serviced for the first couple of years I'd be less worried about it, it's done another 15k and three years without blowing up. It sounds a bit like the previous owner decided after the first service was so long coming that they would have it serviced annually as they feel the same way about the reliability of the sensor based system, but those same sensors will be the ones that make the car run every time you turn the key. I still think that the type of driving has a lot more effect than the overall mileage, a couple of hundred miles on the motorway is a lot easier on the car than a dozen 1 mile round trips to pick the kids up from school, presumably the Mini sensors factor that in too.

Going back a few years (OK nearly 30), I worked for a firm that had just bought a new Merc 308 van, I thrashed it up and down the country for a few months without really thinking about the service schedule, when the thought did eventually occur it was at twice the service interval. We got it serviced and it carried on for many years after that.

Would it put me off buying? probably not, especially if it was in the hard to find spec that I wanted. As MikeGMT suggested, huff and puff a bit about the 'missing' service and see if you can get a few bob off.