Jetta Servicing advice.

My Jetta is due for a service this month. It was on long life originally and had a service at 16k a year ago when it was also put onto fixed interval servicing.

Anyway i called my local VW dealership for a quote. They initially quoted me £180 but then said that as it had the service when on variable they could just do a lubrication service on it for £110 this would also include some checks of the car.

I asked if this would affect my warranty in any way and was told that it was all ok. They also told me that they use longlife oil anyway even when on fixed servicing. Is this the case? I don't see why i need to use longlife stuff when it is on fixed servicing. Could i bring the cost down more by using fixed interval oil?

Cheers