SAR Wannabe
Sorry but the old service flew IFR services quite routinely between Penzance and the Scillies. I regularly flew six return trips IFR in a morning or afternoon with an instrument approach at each end. It did not block the whole corridor due to separation because we operated with Culdrose radar keeping an eye on us. St Mary's has an NDB but it also had and will have again an instrument approach using Decca originally and then GPS with a DH of 250 feet AMSL
The problem with IF approaches into Lands End is that even if DH's of 250/300 above the airfield are eventually approved that equates to a cloud base of 650/700ft AMSL and it so often isn't. Even then an approach into the prevailing westerly wind requires the aircraft to fly east six miles past Lands End to join then six miles on the approach adding 12 miles to a 28 mile sector. The helicopter approaches are joined directly from the en route track.