Hi Steve,
Seems I'm going to go against the grain here but Bamburghs such a well photographed subject that I've seen some stunning images of it...unfortunately for me this isn't one of them, I'll give reasons of course..
Lighting.. by your own admission the lighting is flat and colourless so doesn't help you much
Composition...no lead-in, strong foreground etc to strengthen the shot, the castle is also very central
It's a great subject for sure and one that would well be worth revisiting for better light if you get the chance. Sorry to be negative but it's just my opinion
Simon