Boulby is hot and dry, also gassy in parts.
I went there about 15 months ago for reasons of my own and I usually wear a pair of short cotton pyjamas under overalls, they cost about £5 in Tesco's and are just the job for that kind of thing.
I also wear fairly heavy socks with rigger boots, I find they are more comfy and don't chafe as thin ones do when your feet sweat.
The lampbelts there have a pouch on them for a bottle of water, which you do need.
''the stopes soared beyond the range of our caplamps' - David Bick...... How times change .... oh, I don't know, I've still got a lamp like that.