So, in a spirit of enquiry, I connected this loco to 12v DC. Runs like a champ, reverses from the transformer too (interrupting the power cycles the reverser).
I’ve got a “dumb” tender I converted for the Berkshire, so that will probably be the easiest solution to the whistle issue. That, or I’ll reverse the wires at the handset.
I don’t find the leading bogie and motion particularly difficult to work on, they are much like the Scout 2-4-2, although you definitely need to pay attention while refitting them!
I think it’s a super piece of kit, strong and robust. I can run it around the tree and not worry about little hands getting hold of it!