If you are happy to just rely on the plans, then that is fine: save yourself the money and don’t get us out to site.
Do keep in mind, however, that plans from Dial Before You Dig are only provided to give you a guide to the presence of underground utilities in the area. If you need to know where exactly onsite each of the cables are, then you really do need to get a cable locator onsite.
Also, don’t forget that the majority of things shown on the Dial Before You Dig plans will be mains, not individual home services. If you get us out to your site we should be able to locate all the individual services as well as the mains pipes and cables.