Pogo

Hi, I currently have a full time job with the basic tax rate of 20%, all pretty straight forward but have invested savings into fixed bonds which pay out approximately £12000 per year in interest. Will my tax code automatically be adjusted under PAYE or do I need to contact the HMRC? There are a lot of conflicting numbers on the internet of what can be earned before being taxed on savings. How much can I earn in interest on my savings before paying tax? How will this tax be payed, through my PAYE tax code or by some other means?