Nick,
I used the "preferred current source" found on Rod's page.
http://sound.westhost.com/ism.htm
Scroll down a bit to find it. (the actual current source is the part above the "output" of course) This is a pretty common design--you'll need to run it from a negative supply of -20V or more, and use the complements to the transistors shown.
Rod gives the formula for obtaining the current:
I=0.65/Re
Some measurements on your chosen transistors (I used BC546) are in order, but you know that about 55-65 ohms is right for Re. The resistor to ground should be 100K.
I'm still refining this circuit, but it does work well, and with 5% resistors and no attempt at matching provides 24dB CMRR. Omit the current source and CMRR drops to 3dB in this configuration.
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This circuit was developed with the aid of quite a few people on this board. The thread where much of the discussion occurred is "Plate follower and applications".