In reply to j.richards:
*Advice (sorry couldn't resist)
My first thought would be Hollyhead Mountain, not in the pass, but about 30 mins drive from Llanberis, was there at the weekend and really liked the place.
Another option would be to do Slate, assuming you want lower grade routes then Australia would probably be your best bet.
It's also possible (just about) to climb all of the routes at little Tryfan in a single pitch if using 60m ropes, but bare in mind that this will use pretty much every meter of your 60m ropes.
In the Betwys/Blaenau area Craig y Tonnau might be a good option.
All of the above are covered, at least to Some extent, by the North Wales Rockfax.
Going a bit further afield, the Clywd Limestone guide has plenty of single pitch stuff around Llangollen and surrounding areas (Worlds End, Maeshafan Quarry, Pandy Outcrop, Pot Hole Quarry). I haven't actually managed to visit any of these areas yet so I can't speak for their quality.