Engine oil, such a heavily debated subject every time it crops up!
Manufacturers recommend a service interval based on mileage or time, which ever occurs sooner. A car that does very little mileage is likely to have a high water content in the oil due to condensation. So whether you do 2 miles a day every day or 14 miles in one day once a week there's still going to be enough time the engine has been not running in 12 months for there to be a high enough moisture content for the oil to be changed.
Some manufacturers can recommend a long life oil and filter, usually double the standard life items. Some vehicles come with this oil and filter fitted from the factory. Some of these are in fact running-in oil mixtures and the filter has a different valve inside it for the running in process. Obviously the engine is partly (usually 70%) run in, but as a cost cutting measure this is what they came up with.
(this ends the scripted bull**** I had to learn to say to customers)
Changing your oil more often has no bad effects, only those on the environment and your bank balance (I suppose you could say the threads on the sump and sump plug will have more wear!). If you are with it enough to be using your vehicle outside of the average trip to work and back and to the shops at the weekend then you should be with it enough to adjust your service requirements.
Anyway, don't think i would have done that work for much less than £500 so that's a no bad deal you got!