There are three modes that occur with great regularity in the collected repertoire of melodies of British isles[geographical DEFINITION]. They are Dorian ,mixolydian and ionian, that gives a certain limitation to the variety and a certain amount of repetition musically.
Dives and Lazarus,[imo] is closer musically to star of the county down lowlands of holland and van diemans land than Brigg fair.
A L Lloyd may have stated something over 50 years ago, does that make it Gospel? I rely on my own ears, not Lloyds scholarship. yes most tunes in the repertoire are in 3 modes and fall in to certain musical families and some are used over again,some have bits of phrases that occur in others , some have two bars or four bars that are the same.
this kind of musical analysis can be useful in learning tunes,but in my opinion can remove some of the beauty of the tunes and be reminiscent of the quote by Oscar Wilde
someone who “knows the price of everything and the value of nothing”