I've just noted that Pugh dates the Woodbury Hill affair to 1405, whereas Davies puts it in 1404 and questions whether it even happened. I followed Pugh in Fetterlock, but where historians differ, how is a humble novelist to know? According to Wylie, Henry IV was in Worcester in August 1405, but not in 1404 as Davies states. Looks like Davies may be mistaken here, unless his instinct that it never happened at all is the correct one.
Anyway, the French departed, and Henry IV's government began to achieve progress. In Autumn 1406 the submission of Anglesey was completed and the population made to sue for pardon and pay fines. They had been taking a major hit from Anglo-Irish raiders and it was all too much. The fall of Anglesey put the squeeze on Owain's supply of food, as it was one of the most productive areas of Wales. In addition it was now much easier for the English to mount a sea blockade of the remaining rebel strongholds of North Wales and cut off supplies to Harlech and Aberystwyth.
As mentioned earlier, a siege of Aberystwyth was abandoned in 1407 despite the sterling staff work of the Duke of York, but nevertheless it fell in the late summer of 1408. In February 1409 the last stronghold, Harlech fell to Gilbert, Lord Talbot, and his brother, John Talbot, Lord Furnival, later to win fame as Earl of Shrewsbury and father of Lady Eleanor Talbot.
Owain's wife was captured at Harlech along with her daughter Catrin, Catrin's children, and other members of Owain's immediate family. Sir Edmund Mortimer died during the siege, some say through starvation. (There is also a legend that he escaped to Scotland, but it's almost certainly just that.)
Thereafter Owain's rising was reduced to a guerrilla campaign, though his followers were still, for some years, to prove capable of producing scares and shocks. Owain was never captured, and died apparently in September 1415, though no one is sure to this day where he is buried. (There are several theories.)
The last of his six sons, Maredudd, continued the struggle in remote Merioneth, and as late as 1417 the rebel Lollard, Sir John Oldcastle, tried to make contact with him there, only to be captured en-route by Lord Charleton of Powys.
Maredudd was offered a pardon that same year, but didn't accept it until 8 April 1421. According to Welsh legend some of Owain's followers continued the struggle after that, right through to the arrival of the 'redeemer' Henry VII. If they did, it would have been hard to distinguish their activity from that of routine banditry.
If anyone would like more detail about Owain without getting a book out, there's a useful site here.