Seaford Museum has an excellent radio and electrical display. Only open two hours a week, but worth a visit:
http://www.seafordmuseum.co.uk
Also Orkney Wireless Museum, a bit remote but very good:
http://www.orkneywirelessmuseum.org.uk
Finally, the Telegraph Museum in Porthcurno:
http://telegraphmuseum.org
I've visited all three and can highly recommend them.