[Peter86]

Car oil isn't that expensive, at volvo anyway. My Volvo dealer sells me 4ltr castrol edge 0w30 at £24 with vat. 1 ltr bottles are £12, why so much more I don't know. They will probably be charging you by the litre on the service, plus volvo labour rates. At my dealership older cars get better discount, newer cars get very little till about 3 years old.
I signed up at the parts desk for discount, last time it was in for a job, got the quote, they rang the parts on my behalf, asked for the discount, saved about £90 total on new alternator, aux belt and aircon belt. Don't get discount on labour though. Still not trade rates but still I saved.
Pop into the parts or give a call and see if they give discount on your car, takes 5 mins of your time.

Another good option that someone I know did was buy a 5 year service plan with the car. Worked out at £100 a service. Now his cars 5 years old he's going to ask if he can buy another plan.