Another Student of Mr Zaks eh!! Me too and Lance leventhal, but remember Their work is z80 based not zx81 and as the little door wedge is wired in a very non standard way not all examples work.
A few other useful sites..........
http://www.retrocomputermuseum.co.uk/forum/
A forum member called Womble Is from Your part of the World (Yes I Know Oz is bloody massive)
The German ZX81 forum.........
http://forum.tlienhard.com/phpBB3/viewforum.php?f=2
Google translate v useful here
And for trading..........
http://www.sellmyretro.com/
Rich Mellor who runs the site I find to be a good honest trader ( crap I owe Him some feedback!)
Read all the threads Oscar, some good stuff going on, and if Your house lights go dim It's just Lord morris ( should be Sir Morris But I'm in His debt) or Andy Rea switching in another generator to run their latest projects!
regards Moggy