Culdrose is slowly getting depopulated with aircraft. Once the Sea King finally goes there will be two very new and shiny hangars and squadron HQs empty, which will probably be filled with the rest of the Merlin force. This will leave B site empty.
Not sure of the runway lengths for P-8 or P-1 ops, but I've seen A320s, Nimrods and Globemasters all happily using it.