On my recording - "George Blake's Legacy" - I have it as collected from Blake as below:

THE ROCKS OF SCILLY.
It’s of a brisk young seaman bold that ploughed the raging main.
Come listen to my tragedy, while I relate the same.
It’s pressed I was from my true love, She’s the girl that I adore,
And sent I was to the raging seas, where the foaming billows roar.

We had not sailed a league on sail before a storm did rise,
May the Lord have mercy on our souls, so dismal was the skies.
Sometimes aloft, sometimes on deck and the other time below,
When the thoughts of my Polly love run in my mind when the foaming billows roar.

Our Captain being a valiant man he on the deck did stand,
“Here’s a full reward of fifty pounds for the first that could see land.”
Then up aloft our boatswain went on the main topsail so high,
He looked around on every side, neither land nor life could spy.

The very first time our ship she struck so loud against a rock,
May the Lord have mercy on our souls for the deep must be our lot.
And out of eight hundred seamen bold only four got safe on shore,
Our galliant [sic] ship to pieces went and she was never seen any more.

And when the news to Plymouth came, our galliant [sic] ship was lost,
Caused many a brisk young seaman bold for to lament her loss.
And Polly dear she must lament for the loss of her sweetheart,
’Twas the raging seas and the stormy winds caused my love and I to part.

Gardiner mss. no. 344, and it would seem that the text for this song was collected on two separate occasions with very slight word changes, first In June 1906 in notebook no. 7 page 61 and then November 1907 in notebook No. 12 page 101. Blake’s title in the manuscript of 1906 is “It’s of a Brisk Young Seaman Bold”; only later is it called “The Rocks of Scilly”.
However, it does say that Mr. J.F. Guyer collected the tune in November 1907. Roud has it listed as no. 388 in his index and a version collected by Gardiner from George Collier of Street, near Petersfield can be found in Purslow’s Constant Lovers on page 87, Gardiner mss. no. H1135. The text and tune are different to Blake’s. In fact Blake’s tune is a version of the well-known tune: Star of County Down and its alternative titles, which Gardiner in his notes calls “The Marigold”. Many singers have used this tune for
many different songs all across England and even North America. The chosen text here is as collected in June 1906, mainly because George seemed to have fuller texts earlier in his life, even though he was 78 in 1906.

Tim Radford