40a Russian poet and author of Boris Godunov? (7) 37d Surrey town renowned for horse racing? (5) 16a Sucking eel-like vertebrate of the family Myxinidae? (7) 28a Hungarian film making partner of Powell? (11) 30a Musical instruction to play in a brisk, lively manner? (7) 32 Fatal disease for herbivores with symptons including fever and enlarged spleen? (7)