Planning your new kitchen is usually a straightforward affair. Most modern houses don't really allow much scope for changing the layout from what is already installed. Doors, windows and services such as electricity, water and gas nearly always dictate where important items such as cookers and sinks are going to be placed. If you are going to fit an extractor hood and decide to vent it externally, be sure to check what is on the other side of the wall. Common obstructions are the ends of window lintels, garages and low eaves.
Using a tape measure carefully measure your kitchen, remembering that tiles can be up to 10mm thick. It's a good idea to measure the same wall at different heights, walls are very rarely perfectly upright. The distance for the base units is quite often different for that of the wall units. Trying to squeeze a unit into a space that is 5mm too narrow is impossible.
Most kitchen brochures will have the unit dimensions printed in them. Using this information will help you fill all the available space even if it means fitting a unit of an unusual width. Amongst this information is usually the corner unit dimensions, it is critical that you understand exactly how each corner solution will work. Each manufacturer uses their own sizes for the corner posts, so just because your existing kitchen fits round the corners doesn't mean that your new one will. If you have any doubts you should always contact the supplier for advice, the last thing you want is the handles on the drawers catching or your new dishwasher refusing to open.
If you require any changes in either your gas or electric supplies to your kitchen you should always use the services of a qualified tradesperson. The cost of these works is sometimes rather high so be certain that you really need to alter these items. Never be tempted to alter either gas or electric supplies yourself in order to save a few pounds. The results could be both dangerous and illegal.
Careful planning and design will lead to an easy installation, exchanging units is never straightforward and can hold up the installation for quite a few days.
If in any doubt please talk to an expert.