I have an acceptance letter from a Uk University, and I have until February 2 to accept it. I was wondering what happens if I decide to accept it, and afterwards recieve an offer from a second University.

Can I reject the first one after acceptance?
Do they communicate so that all universities in the UK become aware of my first acceptance?

Yes, you can reject the first offer afterwards. There is no issue of communicating your acceptance to other universities,no such system exists plus the admission process in the UK is stricly confidential!

Thanks for your help Ida!