Apologies for the self promotion... I loved Defender as a kid and played it endlessly on the BBC Micro under the guise of Planetoid... so I've written something as close to the original as I could including most of the in-game sounds. Hyperspace and bombs are there too.
I'll try and get a youtube video of it but here are some screenshots:
http://www.faulconbridgesoftware.com.au/
Hope you enjoy it!