All surgical procedures are associated with an element of risk. Your surgeon will explain the risks for a circumcision to you in your consultation and will give you the opportunity to ask questions.
In the UK, complications after adult circumcisions carried out for medical reasons are rare and most men don't experience any significant problems. Apart from the initial swelling, bleeding and infection are the two most common problems associated with male circumcision, however these are rare and can be easily treated and managed if they do occur.
With the removal of your foreskin, the end of the penis will feel different and you may have less sensitivity over time.