Thanks for your valuable input, Nick, I was hoping you would email me!
I am collating responses to the questions and issues raised - one of which is Birstall. I am actively exploring this option, but so far have met with surprisingly little support for a relocation back to Birstall even if it were possible on either of those alternative nights. Also it needs a proper recce to the BB first - so is there anyone better placed geographically than I am who could do that, I wonder?