The UK has implemented Council Regulation (EU) No. 833/2014 of 31 July 2014 through The Ukraine (European Union Financial Sanctions) (No.3) Regulations 2014. The latter is in force as of 1 August 2013 and can be accessed here.
HM Treasury has also published additional guidance regarding restrictions related to transferable securities or money-market instruments, the arms embargo, the export ban on dual-use goods for military end users and the measures to curtail access to certain technologies. This guidance is available here.