If you approach thru' the woods (turn left at the gate out of the car park rather than going down to the beach), follow the track past a small lake (or big pool... whatever you will!) raised hide with walkways, n' through the back yard of an old house, you'll eventually spot another raised hide on the edge of the wood... you can get a good view across the camp from there.

There's a track that leads across the marsh back towards the road and past the camp. It's still quite well defined with good deep ditches and a raised causway leading off into the woods (which the hide stands on). I'll post my pics when I get them developed.

Caistor St Eds is only about a 5 min drive from the henge. I think it was established by the Romans after Boudicca's revolt was crushed... I'm not sure if ow't stood on the spot before. It'd be interesting to find the settlement and field systems of the people who built the henge... they must be fairly nearby!