The 139 doesn't carry MRT, MIRG, 2 stretchers plus a doctor, hovers 8 degrees nose up and has all the SAR kit stuffed down the tail because there isn't room in the cabin and is awful on sloping ground due to poor clearances. What will change with the 189? Yes they both go fast but for the most part that isn't what SAR is about.
For once I agree with Crab. The AW139 is inadequate for the job but has been made to work by the persistence and determination displayed by the Lee and Portland crews. The AW189 is a sop from the treasury and MCA because they know the S92 is better suited to the task.
On the matter of Portland being closed, remember that Lee covers their patch from 21:00 to 09:00.