A battery service where they replace the battery, replace all the seals and then clean (not refinish) the case and bracelet is around £85 - full service when they refinish and service (plus replace the battery) is about £230 according to the Breitling website.
Worse case if the movement needed replacment for some reason then you would be looking at a bigger bill.
I have owned 2 for the last year / 18 months and they are great pick up and go watches. There is no reason why you could not get a competent watchmaker to do the battery change for you but as the cost is not horrendous in some ways its good to get the stamp in the book when Breitling have done it.