There is a new pontoon with space for several boats (and more when rafted) in the outer harbour at Church Bay, Rathlin Island.
Local people told us that the outer harbour has been dredged, and is deeper than the inner one (which I believe is about 2m on the SW side). I was told that it costs the same as the inner harbour at £6.50 per night. Electricity meters have been fitted for power take off, although the remaining unwound half drum of cable may indicate that the work hasn't finished yet (July 2005).
The outer harbour will feel the swell more in a southwesterly, and there is a a lot of RIB ferry traffic coming and going. However it avoids the rocky bar at the entrance to the inner harbour.
More in Silkie's blog at http://www.yotblog.com/Silkie/273.