Hi Charlie,
The 3rd Edition of Waring, Townsend and Lewington now names f. juncta as f. tutti and explains in some detail the suggested differences between D. chrysitis f. tutti and D. stenochrysis (which are IMHO very subjective) which is still yet to be confirmed for the British list. The NMRS only reports D. chrysitis to the specific, ignoring the form names.
However, I suspect if-and-when D. stenochrysis is confirmed as British, confusion and conjecture will arise and for many specimens it won't be possible to separate D. chrysitis f. tutti and D. stenochrysis in the field thus requiring an aggregate.
Colin W. Plant, the Hertfordshire County Moth Recorder has written a couple of lengthy notes in the Entomologist's Record re D. chrysitis and D. stenochrysis which goes into even more taxonomic detail. I don't have any references to-hand but an email to Colin may be quicker than waiting for me to find them!
Les Evans-Hill
Senior Data Officer
Butterfly Conservation, Butterflies for the New Millennium and National Moth Recording Scheme