I also suspect that the height issue at Keswick cainebj knows about will be the reason for 16184s departure, and presumably 16185 when it gets an engine.
thats if that bridge is an issue for them! i've got a feeling the height restriction is 14'10, which i believe is the height of them Palatine's! could be a bit tight taking them through! (they've both been seen on the 555 down Lancaster end, but i've never heard of one being seen on 555 at Keswick end!)
havn't been near that bridge for quite a while now, with it being on the way into Keswick for 555 (and TransCumbria from Penrith). i havn't been to that side of the town.