Ren, I find the effects to depend so much on the power coming into the amp, the power cord, and the entire tube complement that it is hard to make a general statement. In the SEWE300B I rotated the three different tube types and different brands of the tube types, and decided for MY system using three 75C1 (which is a variant of the OC2, a shorter tube with a dark lining) to be the best--it gave the most power as well as a focus that was not hard or sharp, or too soft. When I had the SE84UFO3 monoblocks I found 0D3 to work best for the output tubes and 75C1 for the input tubes. Others made other choices.

You could make a query to Sarah or Veronica to see whether they could sell you three tube types in sets, or I have always easily found examples on ebay.

Dom, no I do not BUT I have bought several handfuls of these tubes and they all seem to look and sound the same, and all that are marked with any country of manufacture are . . . marked Great Britain or England.

I don't think you can go wrong with these tubes. I'll be interested to hear what you think of a pair in action!