Yep, it's limestone, but not like any other I've ever seen. The rock faces are almost flawless with only small pockets as holds, occasionally there are cracks but these are few and far between.
And yes, we did climb them, although not the ones photographed here. I did a couple of the classic sport routes (Tales from the River Bank and On Some Faraway Beach; both fantastic) and then spent the rest of the day bouldering. It's a great place to visit, even if it's just for a walk; I can highly recommend it!
"The happy climber, like the aged Ulysses, is one who has "drunk delight of battle with his peers", and this delight is only attainable by assaulting cliffs which tax to their very utmost limits the powers of the mountaineers engaged."
--A F Mummery