Gary

You can buy PVC scotia or quadrant mouldings from fascia dealers that will bend and flex to the shape you want. Only problem is they are White, but this looks fine if your skirtings are White too.

Condensation is almost always because of a lack of ventilation. Are there sufficient soffit vents, more of these will help and be the easiest and cheapest option.

The hammock you're talking about I assume you mean when chicken wire is laid over the ceiling joists in between the ceiling material and insulation above. I think this is a building regulation issue, usually required over old lathe and plaster ceilings to prevent in the event of a fire the flammable insulation falling down with the ceiling onto people upstairs, or firemen fighting the fire.

If your kids are going to be up there playing/banging around and you have lathe and plaster that collapses easily it's worth considering.