All the above look like good suggestions. Would add
https://www.solentsky.org in Southampton, quite "doable" in a day by train, if they are operating, from Waterloo Stn in London. Would echo the advice to check opening times over the Christmas / New year period.
Enjoy your trip what ever you choose to do. Oh, the "fired up" Lightning could be a challenge too far...Used to be done at Bruntingthorpe but now closed.....