I have a very close friend (old school buddy from waaay back - about 49BC!) who did exactly what you are trying to do and the following is based around what he has told me.
All the kitchen fitters I have come across use the same (or very similar) carcasses, units, handles, appliances and surfaces. This is OK at the Wikes/B&Q end of the market, but that is a very thankless end to fight in, as it is far too price-sensitive, i.e. little or no profit!
Your number one priority has to be a good and professionally built website, featuring professional photographs of kitchens that you have built. Never ever skimp on photographs and never imagine that, just because you are the proud owner of a DSLR, you can take good photos of kitchens. (I used to labour under that impression, because I have worked as a professional film and TV cameraman.) Trust me, product photography and stills photograph in particular is a completely different discipline and uses completely different lighting and composition and is a discipline that very, very few really master. And to top it all, kitchens are very hard beasts to photograph well!
You will also need some printed literature, nothing too fancy, but again featuring work that you have completed.
Stick your message and links to your website, etc. all over places like Gumtree and any other local listings.
Offer the punter things that they cannot get elsewhere. For example, I have a proper catering sink in my kitchen at home. It is a large 2.4m double sink with double draining board from Nisbets and I have put simple white doors and shelving below this with sexy wooden handles. Not only is is extremely useful, but it is the focal point of the kitchen.
When designing the kitchen, offer the punters things like wood-burning stoves and different types of hobs (e.g. mixed halogen and induction). Also, many people look at professional kitchens on TV, with drip-free hose-taps, griddles, Salamanders and deep fryers with envy and of course never see anything like that in any kitchen showrooms. Offer them the ability to build stuff like that into their kitchens (if that is what they desire!)
Most domestic kitchenware and appliances are pretty useless. They sort of work, but not properly. Offer or advise that the punters opt for decent stuff. Air extraction systems that are silent, dishwashers that do a full load in half-an-hour, ovens that do both air assist and air only baking, gimmick-free refrigerators that are totally silent - whatever they put into their kitchens has to be a joy to use, not just when it is new, but in ten years time!
Cover and advise on everything. Floors, walls, electrical installation, heating, water and air, the lot. Lighting is very, very important! Our kitchen has 20 power points and nearly all of them are in use.
Very often, the entire room needs to be renovated and/or made suitable for a kitchen and you should be able to cover all that kind of work. New water and drainage lines, electrics have to cover 30 amp hobs and ovens and other circuits for fridges, fryers, grills and coffee machines, as well as a parking space for mixers, blenders and all that stuff.
Every kitchen you build should be your salesman for years to come. "Oh Henrietta, where did you get that sink? And I just love your wood-burning stove!" says Henrietta's friend June.
"Ah!" says Henrietta. "There's a chap called Scott and he sourced and installed everything for us. He even made this fitted shelving unit that you can pull out and it turns into a serving trolley! Oh and have you seen this clever unit here - it just pulls out and can hold enough wood for the stove for three days! He also made this incredibly clever space here, where I can leave all the blenders and mixers plugged in, so I don't have to go digging them out of a cupboard and fiddle about with plugs and sockets!"
June now wants a new kitchen and on Henrietta's recommendation, she comes to you! Only she wants everything hidden (because she saw something like that on 'Grand Designs'!) and she wants things to rise up out of a central island as if they are models on Thunderbirds! And before you know it, another kitchen is helping to sell your services!
According to my friend, selling kitchen design and fitting is like a ketchup bottle - first nothing comes and then a lot'll!
My friend also offers his clients an annual cleaning and decorating service. Kitchens get manky and start to look tired after a year or so and most families do not want to redecorate and deep clean the kitchen and muck about with changing neon tubes and LED lights leading up to Christmas, any more than they want to service their own cars and do an oil change themselves. His guys come in at nine and by five o'clock, the walls and ceiling have been repainted, the floors are spotless and lights and other fittings have been cleaned and/or replaced.
But he does have a showroom.
