CREATE TABLE table_13917 ("Year ( s ) " CLOB, "Selection show" CLOB, "Venue" CLOB, "National final main host" CLOB, "National final co host" CLOB, "Semi final/heat host" CLOB)

What is the name of the national final main host at BBC Television Centre, and the selection show was Eurovision: Your Country Needs You?
SELECT "National final main host" FROM table_13917 WHERE "Venue" = 'bbc television centre' AND "Selection show" = 'eurovision: your country needs you'
SELECT "National final main host" FROM "table_13917" WHERE "Selection show" = 'eurovision: your country needs you' AND "Venue" = 'bbc television centre'