You will be able to find companies that will do a pumped readymix screed. It may be slightly more expensive but it will invariably be a good level finish and will be completed quickly - a whole ground floor can be done in a couple of hours - plus some preparation beforehand in setting the apparatus needed to get a level finish.
See the Build Process - screeding page
Particle board floor
A particle board floor, sold in sheets 1200mm * 600mm is a very common flooring material. This is the standard for upper floors and the other option for ground floors. For kitchens, utility and bathrooms you will need a moisture resistant grade - but you might as well get that for all the flooring. Usually sold in 18mm and 22mm thickness, the 22mm thickness gives a much stronger floor, unless your budget is very tight. On upper floors these tongue and groove boards are generally glued together as they are laid and nailed to the joists (a nail gun makes this a relatively easy task). For the ground floor there are two main ways in which it can be laid.Floating Floor
A floating floor uses particle board that is laid onto the insulation sheeting. The tongue and groove boards are not fixed to the underlying concrete or beam/block. They are, however, glued together (PVA glue). One can imagine that the grand piano may tend to dip the floor where the polystyrene may compress slightly. Using 22mm board instead of 18mm will reduce this tendency but, to make it more rigid for the grand piano, a battened floor is better. For the kitchen and utility rooms, where you want the floor standing units to sit on a firm floor, it is best to use battens anyway.
Battened Floor
Battens are screwed to the underlying concrete or beam/block and the insulation sheeting is cut to fit between the battens. The particle board is then screwed or nail gunned to the battens. The use here of 18mm boiard is quite acceptable as it is well supported on the battens.This creates a very solid floor with the warmth afforded by the insulation. But, it is very labour intensive. Just cutting the insulation takes a long time. The battens can be screwed into the concrete using either frame fixings or special screws which are designed to screw straight into concrete, once a pilot hole of the right width has been drilled. The battens are set 400mm apart, but make it 300mm for the kitchen/utility room. For kitchen, utility, and any room with sanitary ware, use a moisture resistant board - but you might as well use it everwhere - some builders merchants will supply moisture resistant as a matter of course anyway.
On a block and beam floor, the battens will be laid across the beams, and fixed into the blocks, not the beams!
The process is to be seen in the Build Process - floorboarding page. These photos show the care to be taken to get the kitchen floor very level, which will eliminate any gaps between the kick board and floor.
