The idea of doing a "service" on a bike is batty anyway; it's not a car where you need to change oils and filters and not much else. A bicycle is a collection of systems that need to be tweaked and kept in adjustment to get the best from them and the only way to do that is to learn to do it yourself.
I despair when I see people posting that their bike "has just been serviced " and they expect it to be running perfectly. You will only know when a something needs attention if you are attuned to the sound and feel of it or if you take the time to inspect it carefully; which you can't expect a mechanic in a bike shop to do when he's under pressure and being distracted by colleagues, customers, loud music and his mobile phone.
Bike "servicing" is a boring, tiring, tedious job that makes no profit no matter how much the shop charges. Speaking as a bike fettler who has tried, briefly, to make a living from servicing bikes, there's nothing more depressing or de-motivating that receiving a bike in a filthy neglected condition from a customer who expects you to wave a magic wand and make it like new again, especially when you know that your efforts won't be appreciated and they will continue to abuse and neglect the bike.
The simplest and cheapest answer is to buy some tools and learn to do your own maintenance. That way, when the bike breaks out on the road, you've a better chance of fixing it yourself.
