It's a lovely position to be in, and having been there myself I would say try not to get too much fixed. If you're allowed, get moveable computer areas, moveable dividers to make reading corners or role play areas. As soon as things are fixed it becomes limiting. However, in our extension anything that was fixed, the LA paid for, anything not came from the school budget so you may not have too much choice!
Think about your main areas of movement e.g. To the door, from the cupboard to your whole class teaching area, the route to the toilets etc. then think about your more static areas and put fixed items there.
Storage! much like new houses, new classrooms tend to be short on storage so make sure you look at that -will you get a cupboard, shelves, under sink space?
Height, double check the sink etc is at the right height for your age group. Ditto any display boards - do you want them at the same height (child height, adult height?) or a mix?
I'd be tempted to ask for Lino throughout (esp if you're having underfloor heating) and then ask for a an enormous rug if you want a carpet area. Again, then you can move it and try out different room arrangements.
I'll have a think when I'm more awake and be back if anything else comes to mind!