The variations found in what is known as 'Peacock's Collection' form one of the most challenging parts of the NSP repertoire. They are difficult to perform adequately, requiring every resource of intelligent articulation to make the repetition and development they contain musical and interesting. Troublesome to play but extremely rewarding when things goes well.
Some questions: What is the probable context of these particular variations; is any one of them known outside the Peacock collection or do they all seem entirely of his own composition? If as has been said, Peacock probably played them through and Wright, the publisher, notated them, are they likely to have been improvised and rehearsed for that occasion or did Peacock reproduce something that he commonly played? Improvisation nowadays seems pretty much a lost art outside the jazz field though it may well exist in musical areas where I just don't go. But it was very much of the musician's art in earlier days. The art of variation exists also, of course, in the ear of the intelligent listener.
At present those pieces are regarded in a fairly scholarly and literal way, in a manner that would not have been originally intended; the content, order and number of those variations may have been a highly variable thing, depending on the mood of the player and whoever may have been listening.
Perhaps there are some clues elsewhere in what is known about fiddle variations of the time. But the best evidence probably lies in the music itself. Would anyone who has really explored this repertoire like to respond to this ill-phrased enquiry?
Francis