This is actually a trad song in the Sharp Mss and it's also in Sharp/Karpeles (Vol 1, p501) so it's a good candidate.

Here's the Catnach broadside in Madden.

It's in dialogue form so likely from a musical play or burletta.

Henry: Pretty Nancy will you wed?
       Tell me dearest Nancy,
      None but you I have always said
       I could ever fancy.
             Sing fal de ral, &c.

Nancy: Till I find a faithful youth,
         I'll ne'er married be, sir
       Therefore, you devoid of truth
         Have no right to me sir.

H: Why of falsehood cruel maid,
    Do you thus accuse me,
   I never thought by what you said
    You could e'er refuse me.

N: Sir, I've heard and think it true,
    That you are a rover,
   If so. I all thoughts of you,
    Quickly must give over.

H: False it is but we must part
    Spite of wind or weather,
    Think not Miss,'twill break my heart,
    I care not a feather.

N: Dearest Henry make me blest,
    Pardon your dear Nancy,
   What I said was all in jest
    Just to please my fancy.

H: Do you love me prithee say
N: Yes! now banish sorrow,
H: When shall be our wedding day
N: (hesitating)Why Henry dear tomorrow
Both: Sing fal, &c. we will wed to-morrow.

(They only partially gave the refrain as the song was currently popular and everyone would know it.)

Here's Sharp/Karpeles.
Version A sung by Mr Hoskyns, Rackenford, Devonshire, 13 Sept 1904.

1. Pretty Miss will you wed?
Tell me, my dear Nancy
You're the girl I always said
That would please my fancy
   With my fal le dal de li di o,
fal de dal de die.

2 Sir, I've heard them think it true
that you are a rover,
If so be the thought of you
Quickly I'll give over.

3 False it is and we must part
in spite of wind and weather.
Think now, miss, to break my heart
For I can get another.

4 Stay, dear Henry, it makes me blush,
Pardon thy dear Nancy.
What I've said I will in just (jest?)
Just to please your fancy.

5 Canst thou love me?
......................
When shall be our wedding day?
Why I think tomorrow.

Version B sung by Wm. Lockyer (87) at Middlezoy, Somerset, 15 Aug 1906.

O pretty maid, will you wed?
Tell me, dearest Nancy
There's none but you I've often said
That ever i could fancy
fal lal la, fal lal la,
Fal the diddle and the diddle and the dido, o.

I could easily post the tunes as they are very simple, but not in standard ABC, but Mick will easily convert. Actually I could scan and send the tunes to Mick or you, Alan.