Try using hot water from the tap next time, it takes longer but it is safer. Run the hot water over the metal just below the plastic head for 5-10 minutes. Do not let the water touch the plastic. It may take longer than 10 minutes, too, so be patient. Eventually you should be able to wrap a handtowel or washcloth around the head and twist it off of the body. When re-attaching the head, rub a little beeswax on the top of the body where the head will attach. This keeps the head from moving around too easily and makes for a more airtight joint.
The very place, and I might pop back soon! Thanks.
My main squeeze has been my Feadog in brass; easy to play, perfect chiff, and I can almost be reckless with breathing. The first time with the nickel fippled Oak made me overblow half the first octave and think this whistle unplayable. It’s now my favorite and it’s difficult to even replicate the tones I first played on it. I have four now. It’s the most consistent cheap whistle I have bought. Thank you.
And thank you, Stuporman, for making me feel almost exactly four years younger!
Oaks are OK, but I don’t believe they grow from Acorns.
And I find that they do not squeek, unlike many of my Burkes, which can squeek when I least suspect.
WTF 
In other words some pretty expensive squeaks.
i had an idea to start making whistles out of the Florida Oak trees down here, and name them Oak whistles. then i started reading and finding out there was already a brand named Oak. 
I have an Oak ‘C’ with a Hoover Whitecap on it…Sweet!