One I've not yet had chance to visit, the Bakelite Museum, but I gather it's good:
http://www.bakelitemuseum.net
Then one I've visited but forgot about, the Montacute Toy, Radio & TV Museum. Many of the radio exhibits were in 'as-found' condition when I last visited, but the nostalgia value of the collection is immense:
http://www.montacutemuseum.co.uk