Yeah Garth and I did quite a bit of bouldering there a few years ago and there is some really good problems to be had, including a really awesome polished roof where the massive holds feel like slopers due to how slick it is. Takes some getting used to. Park officials never seemed worried about us bouldering. Infact we stopped and chatted with them on a few occasions. We stayed away from the main arch, and bouldered in the Coach House arch (I think thats what its called - Nth Arch, not the one on the road)
We also bouldered a bit up the river (Mac something river) from this and yes there is some quite nice looking cliffs upstream which we thought would definately get a look in one day. Trad would be the go with the sensitivity of the area. Damage to cave feautures, Bolting and anchors seemed to concern them the most. Ironic considering the commercial raping of the rest of the area.
There may be some chalk evident still but it doesnt stay due to the colour and surface of the limestone there. Which I guess is a good thing.