I went along and enjoyed it. This is the first time I've been, because this event normally clashes with a local watermill open day (Pann Mill in High Wycombe).
I was amazed to see not one but two pre-war Murphy TVs (A56V and A58V) as well as a working 1948 model, seen on the right of the A58V. There were a couple of Murphy radios made in New Zealand under licence, with different chassis to their British relatives.
As well as the working watermill which is fascinating to watch, there's a museum with a store room that also contains some Murphy TV and radio sets, plus lots of old tools and appliances, like a carpet beater and a gas-fired refrigerator, for example.
I've attached a few pictures. The mill and gardens are pictured on the official website
http://www.welhat.gov.uk/mill