bex698 makes a good point, just check the cost of the parts. Most garages have a good margin on oil, washer fluid etc.
I prefer to do the service on my Land Rovers myself, but that is also because I can use the local LR garages workshop. On the Mini I provide fluids and parts and let them do the work. Hopefully my 500ss will come soon and I intend to do the same there.
BTW 2.6 hours labour for a oil change and change of spark plugs is a rip off. Oil change cannot take longer than 40min so what are they doing the rest of their time? When the Mini went to the dealer for the first service I asked if I could wait? Dealer said that it would take a while but it would be up to me. Waited till the car was in and work started then went around the corner to do some shopping. When I came back the car was ready. On their bill were more hours quoted than the car was in their workshop!!! After arguing the excuse was that they charge the time which is set out in their internal service guideline and that that is an average. Do I care?