The version that I learnt many moons ago from an ex-Shackleton pilot was slightly different:
Shackletons don't worry me
Shackletons don't bother me
With four Griffon engines and flaps on their wings
Bless all their pistons and their piston rings
'though the bomb load they carry is small
Three fifths of five eighths of f**k all
You'll get no enjoyment from coastal deployment
So cheer up my lads bless 'em all.
Now they say that the Shack is a very fine kite
Of that there is no doubt
If you're in Korea with a MiG up your rear
Then this is the way to get out
Just be calm, be sedate
Don't let your British blood boil
Just sit up quite straight
Throttle back through the gate
And smother the b**tards in oil.
Whatever happened to singing in the bar on a Friday night?