Pendennis Castle was part of Flying Scotsman Enterprises at the time and was certainly based there. There are quite a few photos around the system by David Ford on Flickr, which show both locos at the system.
Their eventual move to Carnforth was precipitated when BR wanted to remove the Main Line connection at High Dyke as part of the ECML upgrade.
Allegedly a passing BR Nabob noticed shunting going on in High Dyke Sidings, when they should have been closed some months earlier.
As a clue, the original Preservation Association which coexisted on the site moved to another set of Iron Ore Sidings a few miles away, had a name change about the same time, and still exists today under a (rebranded) name
Regards
Ian