First off, thanks to all those telling me it's inside out (Sorry to Big Stu for saying he was wrong when he first told me a few posts back).
It did make a slight difference to the size, but not enough to matter. I now get a measurement of approx 71cm across the shoulders, as opposed to the 68 previously. The feet are more or less the same as Still Waters' at 46cm (18").
Still a little puzzled, though. Judging from Still Waters' measurement it does appear I have the same bag (less an extra 13cm at the shoulders), but even with that extra 13cm I fail to see how all you big fellas are saying you can freely move about inside? If I zip the bag right up to the limit - which is a struggle in itself, I'm pretty much rendered motionless. Furthermore, because of the quick release zip mech, it just keeps coming undone and zipping down to where there's no strain on it.
Maybe I'm just a fatter ******* than I thought.
You did, you did. I just wasn't aware HOW much of a lump. I'm a tenter, not a bushcrafter, which means I have to do some serious walking if I want to reach remote spots.