I think there may be something to Running in's post:
"We know that the MOD had a major say in the aircraft choice for the new MCA contract. By filling in the gap between Wattisham and Culdrose with small MCA types they ensure that the MOD aircraft will get called to any larger incidents. If S92s had gone into Lee and Portland it would have shown up the obsolescent Sea King with their lower speed and payload.
We know that the MOD are fighting a rearguard action to keep a foothold in SAR, so perhaps they have rubber d***ed the MCA to ensure that they get an increased share of the S Coast action running up to 2012!"
The MOD are struggling to keep their old tired and generally unserviceable Sea King fleet going - some doubt if they will last until 2012. By "helpfully" suggesting that the MCA put small helicopters on the S Coast they will keep Culdrose and Wattisham to the fore. Having S92s in Lee would have meant a large reduction in the MOD medal count and losing jobs to the civvies.
The RAF have committed similar stunts before. When they wrestled control of the RN's Buccaneers and Phantoms (allegedly) they convinced the various ministers and civil servants by presenting a map that showed how land based aircraft could cover all the UK interests worldwide. In order to make the air cover fit the requirements they moved Australia on the map by several hundred miles - hey presto they could do the job worldwide and the RN lost its carriers. Convincing the MCA that the A 139 is a good SAR helicopter is small beer compared to that!