Mmmm, interesting video.
Engine numbers: (I am no expert here but this is what I see).
1951: 101NA - 15808NA
1952: 15809NA - 2500NA and then there was a change in the numbering 25000 - 32302
1953: 32303 - 44134
The number you have provided 27496NA does not fit within these ranges. Is it possible you wrote the number down incorrectly?
I would not change much until you know more, other than looking for more parts and doing research. Who knows what you have may actually be quite an important and a valuable bike.
What you need to do is take photos of the engine, frame and gearbox numbers and make an enquiry to the VVMC http://www.vmcc.net/
Look up the library section http://www.vmcc.net/aboutus/library/FactoryRecords.aspx
and they will be able to give you factory information on the bike. You can also email me with the photos and I will see what I can find for you.
As to the colour "Canadian Blue" as described in the video it is quite possible that the bike was painted that colour after it left the factory. If you contact the VMCC and also include a photo of the bike and the link to the video they maybe able to help.
You can also contact the TOMCC UK http://www.tomcc.org/
with the same information. http://www.tomcc.org/Dating.aspx
Look down at the bottom of the page. They will most properly reply quicker. They have the same info as the VMCC but only for Triumph.
Triumph Bulletin 235 gives the colours of all bike from 1945 - 1962 and that colour does not come up with that bulletin.