Yeah the dealers are buggers. The only reason they carry out a "free health check" is to try and sting you with a big list of upsell parts (brakes and tyres being the main ones obviously). Unfortunatly a lot of dealers have a bonus incentive to the technicians and service advisors regarding how much upsell they can get in a week etc. Shame really.
Thats why I had to quit my post as a nissan mastertech - got fed up with with getting bollocked for not ripping people off every week