There was no explosion
The "explosion" story is most likely a very recent fictional elaboration of a very old "leaking coffin" story. It may be a conflation of this story with stories about the death of William the Conqueror.
No explosion, alleged leakage of fluid from a split lead-coffin in transit two weeks after death.
The earliest known reporter of the leaking coffin story, Gilbert Burnet, seems a little skeptical of it. He says the older accounts were embellished to appeal to the weak-minded.
Modern students of history seem to regard the story as of doubtful authenticity, perhaps having been fabricated.
Henry VIII dies on 28 January. His coffin was moved from Westminster to Windsor via Syon on 14th February.
On Page 20 of Part II of an 1820 reprint of Gilbert Burnet's 1679/1681 "History of the Reformation" it says:
King Henry's body was, with all the pomp of a royal funeral, removed to Syon, in the way to Windsor. There great observation was made on a thing that was no extraordinary matter: He had been extremely corpulent, and dying of a dropsy, or something like it, it is no wonder if, a fortnight after, upon so long a motion, some putrid matter might run through the coffin. But Syon having been a house of religious women, it was called a signal mark of the displeasure of Heaven, that some of his blood and fat dropped through the lead in the night; and to make this work mightily on weak people, it was said, that the dogs licked it next morning. This was much magnified in commendation of Friar Peto, afterwards made cardinal, who (as was told in page 2389 of the former Part) had threatened him in a sermon, at Greenwich, "that the dogs should lick his blood." Though to consider things more equally, it had been a wonder if it had been otherwise. But having met with this observation in a [manuscript] written near that time, I would not envy the world the pleasure of it.
A much later book by Agnes Strickland in 1842 claims
There is an appalling incident connected with that journey which we copy from a contemporary [manuscript] among the Sloane Collection:-
“The king, being carried to Windsor to be buried, stood all night among the broken walls of Sion, and there the leaden coffin being cleft by the shaking of the carriage, the pavement of the church was wetted with his blood. In the morning came plumbers to solder the coffin, under whose feet — I tremble while I write it, was suddenly seen a dog creeping, and licking up the king’s blood. If you ask me how I know this, I answer William Greville, who could scarcely drive away the dog, told me, and so did the plumber also.”
It seems this contemporary manuscript is unidentified.
According to Nancy Bilyeau, "a writer and magazine editor who has worked on the staffs of 'Rolling Stone,' 'Entertainment Weekly' and 'Good Housekeeping.'" :
This story states that Henry VIII dies on 1547-01-28 and his body was in transit from Westminster to Windsor on 1547-02-14 about two weeks later, when, during an overnight-stop at Syon Abbey, after the seams of the lead coffin had been split by the bumping of the rough roads, some seepage of fluids ("blood") was observed and the coffin re-sealed.
The sources for what happened that night are respected, though they are secondary, coming long after the event: Gilbert Burnet’s History of the Reformation of the Church of England (1679), ...
Gilbert Burnet is the main source for the coffin-leaking story. A Scottish theologian and bishop of Salisbury, he is today considered reliable—except when he’s not. One historian, while praising Burnet’s book as an “epoch in our historical literature,” fretted that “a great deal of fault has been found—and, no doubt, justly—with the inaccuracy and general imperfection of the transcripts on which his work was largely founded and which gave rise to
Another history blogger, Susan Abernethy, wrote about "The Legend of the Licking Dogs"
Burnet himself admitted he was in a hurry when he wrote this book and did not research it sufficiently and that the volume was full of mistakes.
This account is well worth reading.