Cheers guys, I was in a real dilema with the FAK, its hardly ever used but......
Mutli tool, yes thats going, it was close to going anyway.
Spare hat, fair point - gone
Spare socks - I would hate to get wet feet on the walk in, but its pretty straight forward I guess. I guess they can go too.
Spare batteries, its two tiny AAA batteries, and if my torch goes.....??
The base layer is a very thin long sleeve one, however, I'm not going to wear two base layers - i sleep pretty hot so that can go.
The flask is very small, same size as a small mug, i figured it is good for coffee, wine, soup, rum, anything really, i can't go without it - I love my mini flask!!!
Alcohol is coming too, however, I feel that the red wine is easier to quaff thatn straight rum, and it's only extra weight for the walk in to the reservoir, which is about 1 1/2 hours I believe, so not too much extra weight.
Cheers guys, it helps to have extra opinions, and make me get rid of things I thought I have to take.