"How big is it?"
It's been many years since I've been to the cave, but I recall the entrance was squareish, each side a few feet long. I can't remember how deep it is, but it can shelter a handful of people.
Apparently, in addition to axe roughouts and chippings, hammerstones have been found. These were rounded, water-worn boulders from the becks in the valley.
The access problems were due to people being ignorant of the existance of the site, and looking for a quick way down to the valley - and it was frighteningly quick in those days. People surfed the stones, resulting in the site migrating further down the slope. Nowadays few use it. It's the descents that caused the damage.
If anyone is determined to reach it, then, in order to cause minimal impact, I would recommend an ascent to it. This will be a shock to the cardio-vascular system, as it's ferkin' steep. Keep to the sides, and where possible the rock walls and ledges. (At this point TMA members of the Langdale and Ambleside Mountain Rescue Team grimace and hold their heads in their hands). Once visited, continue to the top and carry on over the tracks on the fells. A visit to Martcrag Moor can be worth it - I've found axe chippings there, in places where the peat has been eroded away. Also there are sites on Thunacar Knott, Loft Crag, Thorn Crag, and Harrison Stickle
It may be obvious, but take a map and compass, and windproof and waterproof clothing - the weather conditions can change drastically in minutes in the hills.
Take care,
TE