If you really are starting from scratch then you should look at the 'getting started in genealogy' section of http://www.genuki.org.uk/
This is a great site for anything you want to know about researching your family history.
Also try your local library for a basic book on genealogy or family history - and see if your local college runs evening classes in the topic.
The basic technique, from where you are, is;
1. Get all the information you can from living family members. Talk to them all, and ask for names, dates and places, and copies of any certificates or similar documents. Is there a family bible with dates in, for example?
1. Your mother's full birth certificate will give the names of both your grandparents, and where she was born.
2. The date of birth of the oldest of your grandparents' four children will suggest which years to search for their marriage. You do this in the GRO indexes of Births, Marriages and Deaths in London, or at a main library, or at a LDS (Mormon) Family History Centre. More information on places etc from the Genuki site above.
3. Information on ordering certificates is at http://www.statistics.gov.uk/nsbase/registration/certificate...
4. Your grandparents' marriage certificate will tell you their ages and their fathers' names and occupations.
5. Then you can look for your Grandfather's birth, and his birth certificate will give his parents names. If your grandmother was born in Italy you'll not be able to research her that easily - or was she perhaps born in this country to an Italian family?
6. When you get back to 1901 you can look for your ancestors in the Census, which is on-line at http://www.census.pro.gov.uk/
7. And you go back generation by generation in that manner using birth and marriage certificates and the Census (every 10 years from 1841) until the start of Civil Registration in 1837.
8. About 25-30% of the births, marriages and deaths from 1837 to 1901 are also on-line at http://freebmd.rootsweb.com
That should get you started in the right direction. It really isn't that difficult if you approach it methodically, step by step, using all the information you can get from family and from all the documents. But you will need to be patient. It takes a while.
Hope this helps. Good luck with your research.