The argument is certainly based around PFEER - but it is complicated by the agreement between the CAA and HSE over juristication. Essentially the HSE have agreed 'hands off' regarding helicopter operations - so there is no published 'good practice' from the HSE on matters like these - and these days it is the published good practice which really sets what ALARP is - not a quantified risk assessement (i.e the frequency or liklihood is very low so its OK).
Reg 17 of PFEER states that 'effective arrangements are made, which include such arrangements with suitable persons beyond the installation, for - ....(b) rescue of persons near the installation; ... etc
So once you start thinking that the Dacon is unlikely to do more than recover bodies - sitting on the platform waiting for slightly better weather seems like a really good idea!