You can get £109.40 per week Statutory Sick Pay (SSP) if you are too ill to work. It is paid by your employer for up to 23 weeks.
You must be eligible for SSP (external link).
You cannot get less than the statutory amount. You can get more if your company has a sick pay scheme (or 'occupational scheme') - check your employment contract.
There are different sick pay rules for agricultural workers (external link).
There is a separate guide on Statutory Sick Pay if you are an employer (external link).