Personally I wouldn't worry about it. When i bought my 05 GT4 in November, it had only done 25K miles. Service history was not every year but rather on milage, having only had about 4 services. The place i bought it from did service it before i picked it up but it runs sweet as a nut with no issues.
Just because it's only part history doesn't mean it hasn't been looked after. The owner may have performed multiple services his/herself whilst only taking the car in for service when it reached the milage milestones.