Exact ages were much less important in the past than they are now. The census has been carried out every ten years since 1841, and the details are released 100 years later. The 1841 census doesn't record relationships or places of birth. Once you know where some of your relatives were living 100 years ago or more, you'll find that the census is a wonderful source of information, and you can start to build up a real picture of how your ancestors lived. By looking at successive census returns, you can trace the family's progression.
All census returns for England, Wales.
Your local county record office or library may well have a copy of the census for your area. If your search takes you back to the time before civil registration in the early part of the 19th century, you'll want to consult parish registers, as baptisms, marriages and burials then were recorded by individual churches rather than in a central register. The Family Records Centre has many nonconformist registers from England and Wales. The Society of Genealogists in London has the largest collection of indexes of all parish registers, in the country. Another invaluable source of information is the International Genealogical Index compiled by the Church of Jesus Christ of Latter-day Saints , better known as the Mormons.