Image stabilisation either in-camera or in the lense.
Full viewscreen support. - Poor eyesight plus manual viewfinder FTL.
RAW file support.
Preferably to come with a good 18 -55mm lense.
Ease of use - inlcuding any editing software that comes with it.
My budget is around ?450.
First of all, thank you for mentioning a projected budget which many ppl who ask this question always seem to forget. The Nikon D3100 is a very good choice for a new, entry level dSLR. Try one out in the store, compare to a comparable level Canon 500D or 550D (?) and see which controls you like better.
In camera IS: the only bodies as mentioned by others are Olympus and Pentax (choices on cameras and new lenses more limited), some Sony Alpha dSLRs also in body IS. Otherwise with Nikon and Canon, IS is featured in the lenses only. But depending on what kind of shooting you do, IS isn't always necessary if you invest in proper lenses and have good technique.
Full viewscreen support - I assume you mean shooting live view mode on the LCD, basically many ppl will respond: if you don't use the manual viewfinder, whats the point? Seriously, if you plan to shoot with a dSLR and don't want to frame with the manual viewfinder, you might want to consider other options like the micro 4/3rds cameras by Olympus/Panasonic or the Sony NEX or Samsung ILC cameras. Most dSLRs have very slow AF using full live view mode for shooting stills, and its a serious waste of performance potential as well as shooting speed.
RAW file support - they all shoot in RAW, this is a given with dSLRs.
Comes with a good 18-55 lens. Well honestly, most of the kit lenses that come with the camera are the same and frankly, mediocre. So that won't be a factor in your decision making. Once you get your camera you will start saving money for a proper high quality zoom or prime lens anyway.
Ease of use: this depends on the individual camera and your preferences. For this you will have to try them out yourself, that's a highly subjective thing that differs from person to person. I've never used any editing software that came with any of the cameras I bought and prefer to use Adobe Lightroom for 99% of my photo editing. Get a program like that which you can use no matter which camera you buy.