There is the Royal Signals Museum in Blandford
http://www.royalsignalsmuseum.co.uk/ and the TV, radio and toy museum in Montacute near Yeovil
http://www.montacutemuseum.co.uk/.
Also further north is the Radio museum in Watchet formerly at the Washford AM transmitter site/Tropiquaria
http://www.theradiomuseum.com/