Complex sentence: BCS is a member institution of Engineering Council UK, and therefore is responsible for regulation of ICT and computer science fields within UK and it is also a member of the Council of European Professional Informatics Societies (CEPIS).
Split into simpler sentences: BCS is a member institution of Engineering Council UK, and therefore is responsible for regulation of ICT and computer science fields within UK. The BCS is also a member of the Council of European Professional Informatics Societies (CEPIS).