Only just seen this post, Jim! If you'd like my advice like this in future, just PM me, as these days I simply don't have time to read everything that's posted here
Anyway, the answer is yes - this:
English Electric ones from Colomor Valves:
Details here (89 more available, so plenty in stock):
http://www.ebay.co.uk/itm/3707918656...%3AMEBIDX%3AIT
Turns out this company has some history and were taken over by GEC in 1968, see here:
http://www.radiomuseum.org/dsp_herst...ompany_id=8417 The valves themselves are fully NOS, and come beautifully packaged in their original boxes. I suspect that they're 1970s vintage.
Anyway, how do they sound? In a word: wonderful!
In comparison with the NOS Sylvania CV449 I was using beforehand, the English Electric produced a notably more open and 'liquid' midrange, with gorgeous tonal textures and increased detail retrieval. Furthermore, the soundstage/imaging of the Croft seems to have become even more 'widescreen' than before, with music, and particular female vocals, now enveloped in a 'cavernous chasm of clarity', thus increasing their 'intimacy' and believability accordingly.
Honestly, for £6 this is an instantaneous quick, cheap, and very effective tweak for all Croft preamps featuring the use of this particular voltage regulator valve. Highly recommended!
Marco.