SHJ: I may be wrong, but the Shack at the GAM did not look, to me at least, when I visited there in May 2011, like it was capable of running any of its engines.
AFAIK, it's several years since they have been run up (and note that we're talking here about GAM's other Shack, WR982, not the one that's gone to Bruntingthorpe).