Hi, in case you didn't heard the short radio clip on radio 4, the early grand Piano is now back at Apsley House.
http://www.english-heritage.org.uk/about/news/oldest-english-grand-piano-apsley-house/
http://www.bbc.co.uk/news/uk-22507415
I don't know what Temperament it has been tuned to ?
regards Peter B