usually they rip out your kitchen for you - it should be included in the cost - but you should always make sure.
When we had ours done by Magnet we asked them about the flooring. We were going for lino & were advised that it could go in after all the units/appliances had gone in, with a laminate floor, you may want to lay that first throughout so that there isnt an uneveness by the time everything is put in.
Ask a builder if you know one or Homebase themselves.
HTH