He is quoted profusely in the book you gave me. I just checked in the index. In fact, he told the story I enjoyed about Queen Alexandra picking out a substandard McGredy rose to bear her name.
I often wonder how Lady Bird Johnson felt about the J&P rose named in her honor. The blooms are beautiful, but the rose bush itself is a disgrace!
Pickering does indeed carry Dr. J.H. Nicolas, and so does Roses Unlimited. RU, in fact, carries three of his roses: that one, Eclipse, and Mary Margaret McBride. Vintage carries Smiles. I think you should grow some of his roses and The Doctor, which is available from Vintage or RU.