All cars should be serviced according to the manufacturer’s recommendations to ensure that certain parts are checked and replaced when needed to be. Most cars have a service schedule that is split in to miles or years (which ever come first). The majority of cars require servicing every year but many of the newer vehicles have long life servicing which means they only may need to be serviced once every 3 or 4 years.
In a minor service the oil and possibly filer will usually be changed, major components like brakes and steering will be checked. In a major service you may have other filters changes, new spark plugs (if petrol) and possibly cam belt change.
Prices for a service depending on the car, the type of service needed and where you take it. Main dealers will often charge upwards of £250 for a service but your local garage may do it for around the £150 mark. Check your warranty when it comes to a service in case you need to have it done at a main dealer so as not to invalidate it. But if you can shop around you will often get a much better deal.