Peter - I bought the aforementioned Hetch and then saw your post about it. I also received the pics from him and agree it is a Nulli Secundus phase II so 1955-64. I don't think it is a Harry Butler. Where would he get the lugs to make a NS lookalike? Plus, it has the double fluted seat stays which are definitely 50s. I had those on the Experto Crede I bought and sold earlier this year and it was supposedly 1958, and looked it. He told me this was repainted by Argos. Anyway, I only paid 500GBP for it, and either he will sell all the modern parts for me or I will get the whole bike and sell them myself, so can't go too far wrong. It has track dropouts by the way but I can't tell if there is a derailleur hanger on them. It has downtube shifter braze-ons and the wrong top tube cable housing guides. Those will have to come off. I don't care for the paint job anyway so will probably get it partly chromed and paint it in my shop as I have a spare set of decals from David Miller.
Cheers and have a merry Christmas.
Bob Freeman
Seattle