The Bodleian Library Broadside Collection  here has a number of examples of The Rose Of Allendale,  dated (tentatively) between 1819 and 1860.  Although a few small details of wording differ, they are all credited to "Charles Jeffrys" (sic).  No chorus is given; that may have come with the sheet music proper (I believe that copies are extant) or have been added later.  Since Dibdin's work was very well known at the time, that would seem to discount him as a possible author.  That is not to say, of course, that Jefferys may not have based his lyrics on earlier songs in the same genre, as mentioned above.  The Copper Family (A Song For Every Season, Leader Records LEA 4046, 1971) credit the song thus: "words by Charles Jefferys, music by S.Nelson."  If I recall correctly, Mary Black got the song from Nic Jones, who in turn had it from the Coppers.  Jones' recording of the song (with Banddogs) is probably where the "traditional" label crept in.  Interestingly, the tune as usually sung nowadays is apparantly based on a (general) mis-hearing of the Copper Family version; a line of harmony has been assumed to be a melody line.  A few years back, one of the UK folkmusic radio programmes broadcast a version taken directly from the original sheetmusic to demonstrate this.  Regrettably, I missed it, and so have no idea which part it was!  Jean Redpath's version, differing only by a few words and recorded on LOWLANDS, Philo Records PH1066, 1986 (in the database here) also gives the Jeffery (sic)/Nelson attribution, and mentions its publication in A Book Of Scottish Song (Blackie & Son, 1843).  Presumably it was written a bit earlier than that; I'd be very interested to hear any further information anyone may have.  Allendale is in Hexhamshire, Northumberland (England), by the way.

Malcolm