My tuppence worth from my recent experiences:
Unfurnished houses are rare, but landlords are slowly catching onto the fact there is a specific market for them. You can only ask to see if a landlord will remove items from the house - if they don't have somewhere for them they may be reluctant. A large amount of clutter in rentals is fit only for the skip - it isn't worth storing. I would say negotiate over this point, but don't be surprised if you're rebuffed. Many a potentially good rental has been ruined by an awful couch.
- What is the rental market like at the moment - is it possible to negotiate an advertised rent downwards?
It is, but not for every property. Good properties at the right price will let quickly, specifically when you have specific requirements like you (and I) do. If a rental has been up some time and hasn't let then take that as a cue that you might make an offer.
Good quality houses are still a rarity in the rental market in my experience. I viewed one this week that had been advertised for €1600, then dropped to €1350. It's a three bed redbrick. It is a big house and has a lot of potential, but it was stuffed full of old and ugly chests of drawers and bedside tables, and its carpets were filthy. I wouldn't rent it full stop. If you replaced the carpet (it was just in the hall and landing areas) and took the terrible 'furnishings' out of it it I'd have been interested. If the tenants you're after can afford €1350 (never mind €1600) then they can probably afford some bedside lockers from Ikea for €10.