Stuck on three:
16 across: Endurance test centre keeping graduate in contact, say (2,4) _E _A_S
23 down: Central part in God Bless America, no less, or Eric's leading man (5) O_A_A (I keep thing Obama - but who's Eric?)
18 down: Something packed to allow purchase of thread (8) _A_L_L_G
Thanks in advance