How much does a typical third car service cost?

My car is due its third service beginning of next year it will be three years old then it is a ford ka the newer but basic version no central locking etc I was wondering if anyone knows roughly how much it will be for its third service? I've been told that the third service is a big one? Like basic if nothing needs doing i just want to save up every week until then any help will really help thank you!

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