Good luck whoever is doing it. I didi it a few years ago and saw everything from full on gale in the Irish Sea to flat calm off the Scillys and solar eclipse off Lands End. Loved it and hated it both together. Would not want to repeat it on anything under 45 foot and certainly wouldn't set to sea unless 100% confident in my fellow crew. But if it works out it can be one of those big sailing life boxes that you tick off.... hopefully with fond memories!
Have a passing thought for the RORC team that is cast-away on the Fastnet Rock itself for the duration, sitting on concrete and listening to the wind whistling all night and the big ocean seas crashing on the shutters outside.....
Passing thought? We were dead jealous of them all snuggled up in a nice warm and dry lighthouse, probably with a case of something suitable to help while the time away, while we (a bit wet and damp, and drinking tea) flogged our way round the Rock at 0200 in a howling gale 14 years ago......
I would agree with Rob's sentiments above, and once was enough for me.