Is Cat A and Confined Areas a rather rare combination?
The AW139 RFM, and I'm sure many other aircrafts RFMs, has a procedure for CAT A/PC1 confined area approaches and departures so not too rare.
Robbiee - if you don't have HOGE performance, downwind approaches would be very unwise.
The rotor doesn't know it is downwind so any variations in power hovering downwind are to do with overcontrolling on the pedals.
For a safe downwind approach, fly shallower than normal, get the airspeed off early and maintain a sensibly slow groundspeed.
If you are too fast at the end, the temptation is to flare but you don't get any benefit from a change in RAF when you are already downwind.
If in doubt overshoot early.
Make sure you have at least HOGE performance before trying it.