Ancestry is accurate, the only probelm is that between c1920 and 1984, there is no index so you can't search on a name, it is a case of looking at each quarter of each year until you find what you want.
Prior to 1920, most events are covered by FreeBMD and after 1984, Ancestry has them indexed.
For example, I was born 1968 but putting my name and birth year in the search boxes won't bring up any results on Ancestry. I have to actually click on the link that goes to the Complete BMD Indexes, then choose Births, the search for my name in Q3 of 1968. I then get the whole page which contains my entry, and there I am!