Yes I think you have answered your own question. I dont think your 1st service will cost £600 so if it costs £350 then you are £250 up (I've no idea on how much it will cost though). Why do you think you are making a mistake?
As for tyres, you need to buy them when they wear out regardless of whether you have the service package or not.
Edit: just read it again - are you implying you get tyres with the service pack? I didnt think they did a pack like that. I thought the expensive pack covered just brakes as well.
Here we go: http://www.bmw.co.uk/bmwuk/servicepa...312___,00.html
click on "What is covered" no mention about tyres?