To return for a moment to the song.

The well known 'standard' form has been transmitted via print rather than tradition, so the collectors of the early C20 tended to ignore it; they weren't looking for that sort of thing. Nevertheless, it was noted in variant forms by Alfred Williams, Ralph Vaughan Williams, Cecil Sharp and others, localised to Somerset, Northamptonshire and Lancashire among other places. There are a number of mid C19 broadside editions to be seen at Bodleian Library Broadside Ballads; most are set in Northamptonshire, though Lincolnshire isn't far behind. One mentions Nottinghamshire instead.

[The Bold] Poacher[s] or My delight on a shiny night

Localised to 'Zummersetshire', it appeared, with the tune familiar today, in Davidson's Universal Melodist (1847). I don't know if the putative broadside of c.1766 survives, but the following comments from C19 collections provide reasonable background information:

'This song is rather too well known among the peasantry. A friend informed me, twenty years ago [c. 1835], that he had heard it sung by several hundred voices together, at Windsor, on the occasion of one of the harvest-homes of King George IV.'

William Chappell, Popular Music of the Olden Time, II, 1859, 732-3.

'This very old ditty has been transformed into the dialects of Somersetshire, Northamptonshire, and Leicestershire; but it properly belongs to Lincolnshire. Nor is this the only liberty that has been taken with it. The original tune is that of a Lancashire air, well known as The Manchester Angel; but a florid modern tune has been substituted. The Lincolnshire Poacher was a favourite ditty with George IV., and it is said that he often had it sung for his amusement by a band of Berkshire ploughmen. He also commanded it to be sung at his harvest-homes, but we believe it was always on such occasions sung to the 'playhouse tune,' and not to the genuine music. It is often very difficult to trace the locality of countrymen's songs, in consequence of the licence adopted by printers of changing the names of places to suit their own neighbourhoods; but there is no such difficulty about The Lincolnshire Poacher. The oldest copy we have seen, printed at York about 1776, reads 'Lincolnshire,' and it is only in very modern copies that the venue is removed to other counties. In the Somersetshire version the local vernacular is skilfully substituted for that of the original; but the deception may, nevertheless, be very easily detected.'

James H Dixon, revised and expanded by Robert Bell, Ancient Poems, Ballads and Songs of the Peasantry of England. London: John W Parker & Son, 1857.

'W. T. Montcrieff, in his "Original Collection of Songs," London 1850, says of this song, "The writer first heard the old part of this song sung at a small roadside public-house in the little village of Lillishall, Warwickshire (Lillishall, Shropshire, I presume), and was so pleased with the humour and melody of it, that he was induced to add half-a-dozen new verses to it."
Montcrieff introduced it to public notice. It is only accidentally that folk songs have thus been taken up and given popularity.
If it had not been accepted in a music-hall, it would have been unnoticed.'

Sabine Baring-Gould, English Minstrelsie: A National Monument of English Song. Edinburgh : T.C. & E.C. Jack, 1895, ii (notes, 'The Gallant Poacher').

Baring-Gould printed more-or-less the 'standard' version. William Gibbs Thomas Moncrieff (1794–1857; born William Thomas Thomas) was a prolific writer of plays and songs for the London stage and pleasure gardens. His re-write of the song, set in 'Zomersetshire', appeared in his play Van Diemen's Land: or, Tasmania in 1818 (c. 1829; the printed edition was published in 1831).