I'm using Mullard 7062's in mine...sweet. I also have- for backup- a pair of NOS Amperex 7062's,a pair of Phillips E180CC, a pair of GE 12 AV7's and a pair of Tung-Sol 5965's. The Tung Sol and GE's don't sound as good as the 7062 or E-180CC, but work fine in the Exemplar....
The Phillips render great detail, but not quite the presence of the Mullards. The Amperex are not as sharp as the Phillips, but have much of the character of the Mullards.
All are long-life tubes, so my current supply should hold me for awhile :)
Have fun- roll your own!