Oh dear DB - I would love to see you on your high horse trying to complete a mission with a suddenly lowering cloudbase (and you know that happens in the hills and can be very localised) with not enough fuel or suitable weather for an IF abort (because of the task) - if it takes a few hundred yards of careful hovertaxying to get VMC the other side (where the terrain doesn't permit a safe 180 or a precautionary landing) what would you do?
You can't see what the crew are looking at - they are more than well trained enough to assess letterbox situations and what terrain and weather to expect on the other side.
BTW 1 - JSP318 is so last century and these boys are flying a twin-engine, fully IFR capable aircraft with a good AP system - not an unstabilised Gazelle like in BATUS.
BTW 2 - straight from CAP999
Operating minima for the dispatch and continuation of a SAR operational flight are at the discretion of the aircraft commander. However, he is to consider the urgency of the task, crew and aircraft capability and the requirement to recover the aircraft safely