Just coming to the end of mine at BGU in Lincoln – This is the standard core text for most NASENCo courses – a copy of this and you’ll not go far wrong!
https://www.amazon.co.uk/Rita-Cheminais-Handbook-Sencos/dp/1446274195/ref=pd_lpo_sbs_14_t_2?_encoding=UTF8&psc=1&refRID=SF5PEPQ2Z5RC7PGNJ1CQ