My 2003 Flight Guide doesn't say that they won't. They are only open on weekdays, but there is gliding at weekends and evenings, so it looks like someone would be around.
They ask for PPR 24hrs prior to arrival.
Phone nos:- 01326 574121 ext 2415 ATC
01326 574121 ext 2620 PPR/Ops.
By the way, should the title be RNAS Culdrose?