I think all the halls have carpets in the bedrooms, but I know that the carpet in my room in New Hall is not dusty at all (I also avoid dust due to asthma).
As for Fife Park, don't go near it..nah kidding, it's actually alright, just has the reputation. For self catered I would recommend DRA, the kitchens are great and the rooms are nice. For catered, New Hall is great, it has a reputation to be anti social and may seem very big and daunting at first, but after a week or 2 it is great.
There is a wide range of accommodation and prices - you can get a single ensuite catered room, a shared self catered standard room, whatever you want.
As for a flat in town, don't do that till 2nd year, you will make a lot of friends, and most people go for a flat after first year.