Wilfried, (and Malcolm), the Furry Day Carol in the DT has some words very similar to the Halanto from Helston, particularly verse 3 which is like part of the chorus of the Halanto, and verses 5 and 6, but the midi tune is (to my ear) a hybridisation of the Helston Furry Dance tune.

FURRY DAY CAROL

Remember us poor Mayers all!
And thus we do begin -a,
To lead our lives in righteousness
Or else we die in sin-a.

With Holano, Holanto, Holanto,
Sing merry with Holanto,

We have been rambling half the night
And almost the day-a,
And now, returned back again,
We've brought you a branch of May-a.

O, we were up as soon as day,
To fetch the summer home-a,
The summer is a-coming on,
And the winters a-gone-a.

Then let us all most merry be,
And sing with a cheerful voice-a,
For we have good occasion now,
This time for to rejoice-a.

Saint George he next shall be our song:
Saint George, he was a knight-a,
Of all the men in Christendom,
Saint George he was the right-a.

God bless our land with power and might,
God send us peace in England,
Pray send us peace both day and night,
For ever in merry England.

In Baring-Gould's 'Songs of the West', the edition that C# revised and edited, the Halanto words are also set to the Furry Dance tune. The notes at the end say, "The Helston Furry Dance tune was printed in Davis Gilbert's "Christmas Carols," 2nd edition, 1823. His form is purer than ours, which is as now sung*. Edward Jones had already published it in his "Bardic Museum," vol. ii (1802) as "The Cornish May Song," and George Johnson in his "Welsh Airs," vol. ii (1811)."
I would be very interested in finding this version, if anyone has a copy of Gilbert's book.
*That is definitely NOT the way the tunes are played today. The Halanto has a very different tune and the Watersons recorded a version of it many years ago, which we learnt and sang until were sick of it.
But even that is not the way it is performed in Helston these days.
I understand that the Halanto died out for awhile, early last century, and was only revived much later. So is today's Halanto tune the original or some creative work by a revivalist about 50-70 years ago? Should the Halanto words really fit to the dance tune or is the current tune a really old one?
The dance tune, or variations of it,can be found in other carols and even as Morris tunes such as the Castleton Garland Dance and Winster Processional. It appears to be a very widespread tune.
But does it really belong with the Halanto song?

What will I be doing?
I was just going to stay home in front of the computer but then the Wellington Morris people announced a dance-out at my old home town (4 hours drive from here) and I couldn't resist. So I'm off to dance on Petone Beach! (Or, at least, play the music for them to dance.)
Robyn, from Petone