In reply to resqueman:
Hi Dave,
I'm not an expert, but from my experience on the igneous rock in North Wales you will need a lot more nuts than cams - at least two sets. Assuming you have those already, Wild Country sizes 1.5 to 4 (2cm to 10 cm?) are probably the most use. The big ones are good as the nuts don't go that big and I don't like hexes.
On the Orme - I don't know. I've only done sport at Lower Pen Trwyn.
On the slate. Again, a lot more nuts required than anything else. I don't think many people place cams in slate on their first trip. It's very smooth.
Enjoy your trip
Cake