There's been a bit of talk about the Leak tuners in another thread on the Quad FM units.
Here's a site I found some time ago with some useful information, including a TLII schematic for those interested in the inside.
http://werple.net.au/~kiewavly/Leak.html
I have to get me one of these, it's about time I zapped my fingers with some valves
Here's a HiFi World article on the Tim deParavicini Stereo decoder
http://www.hi-hiworld.co.uk/hfw/featureshtml/timdeparadecoder.html
Here's where the Guru's hang out
http://www.gtaudio.com/serv_rep.html
Another stereo decoder
http://www.onethingaudio.com/OTA/9152-OTA-MAIN.htm
Enjoy!