Thanks all.
I'm out! (after 10 hours of back breaking work in the rain)
I took loads of 6' fence posts, my trusty 2cm diameter iron bar, a massive home made maul, a post driver, a bag full of strops and shackles as well as my tirfor.
The anchor point, as suspected, was the biggest problem. It's a semi peat bog and it's been raining for week (yes, yes I *know*, I really should have known better) so the anchor point even though being knocked in good and proper would shift. Through trial and error I ended up having to use 2x posts to 5' depth and the iron bar to get any purchase.
I was a good 300m from the more solid ground, I got a few breaks where I could drive 50m or so before digging in again, even so I needed 4 anchor points before I could scramble out.
Lesson learned! next time I'll go over in the quad.
@anderso: love the tying them together tip; I can see how that would help greatly.
@hughesy: shame about that lack of hard ground