When you are sick less than 4 days running (and off work), you don’t have anything further to do except recover. When you come back at work you should notify your employer that you were off sick and you will be paid as usual for the time absent.
For more than 3 days and up to 28 weeks in one spell of sickness, you can get SSP (Statutory Sick Pay) or claim for incapacity benefits. Ask your employer about SSP and contact your social security office for other benefits. You can also get more information from the Benefits Agency website:
http://www.dss.gov.en/index.htm