There are no cloud/viz conditions at Culdrose that would preclude me from launching on a SAR mission. The wind strength/direction might, ice might. What is relevant before launch is that there is a suitable destination to land any casualties that have been picked up; the challenge of the Met conditions at the rescue site is also relevant, but would not prevent me from launching.
Having successfully delivered the casualties to an appropriate destination (which could be Brest, if that's the only viable destination), the SAR mission is over. If Culdrose is RED/RED the crew should not return to Culdrose. Indeed, on occasions having recovered casualties up Carrick Roads to Treliske hospital, we'd call for the groundcrew to re-cock the aircraft at Treliske, and the aircrew would declare at Alert to RCC from Treliske until Culdrose clears (which could be a day or two later), crew changing as required at Treliske.
Tourist, grobbing into Cu over Looe Bar, or up the Helford, is no way to fly an aircraft that has already finished its SAR mission and is merely returning to base.