GCHQ Christmas Puzzle

I hope you are all working on the annual GCHQ Christmas Puzzle.  I have gotten a running start but the deadline for entries is January 31, so you have plenty of time.  Yeah, I know GCHQ are into the same kind of shady or illegal stuff that our NSA get up to.  But it's still kosher, in my book, to enjoy the puzzles they put out.  Nobody makes fun puzzles like a bunch of crypto-nerds!

No spoilers, don't worry.

The first part was fairly straightforward but required patience and attention to detail.  When I had the A-HA moment about the general nature of what we're looking for, the online references to specifications for such a thing were of great help.  I am definitely going to hide an "Unknown" type Geocache using this method sometime soon!

As for the second part, I do not believe it can be solved in the manner that it makes seem obvious.  At any rate, not without sheer luck.  I found a quick & dirty way to solve it, instead, and I do believe that was the intention of the puzzle-makers.

Now I am stuck on the third part.  Still not ready to throw in the towel, however.  Check in with me after Christmas.