Do I have to register it as a small (tiny lol)company?
Yes, all businesses dealing with food have to be registered and operate out of approved premises. These differ depending on whether you're using pre-prepared products or preparing food from scratch, but the Sanepid website says that domestic kitchens do not satisfy the requirements, even though the EU regulations specifically allow for this option. For some friends of mine who run a small wine bar where they also prepare food the requirements included 2 entrances (one for food/wine deliveries and another for the clients), tiling of the walls, washable floors, separate sinks for washing hands, utensils and preparing fruit/vegetables, an industrial standard dishwasher (with a certificate) and a separate sink for rinsing dirty dishes located in a separate area, a HACCP assessment showing the production route and packaging and storage that is certified for food use. If you plan on using fresh eggs you need a steriliser set up in a separate room for sterilising them (otherwise you can buy pasteurised eggs in cartons). If you plan to transport food you need to have an approved vehicle (refrigerated, if the food is perishable) and facilities and procedures for cleaning it, as well as a separate area for washing out the containers used for transport if they're reusable. You may also have to keep samples of your food for a certain amount of time. Every year you also need to get your water supply tested (600zl) and have a Karta Zdrowia for anyone handling food.
Forget about getting any useful information out of Sanepid - they are there to inspect you, not to help set you up so that they have less work. You will need to get a specialist architect to do the design which is then submitted for approval. You can't start doing business until your premises have been approved.
One way around this might be to set yourself up as a cake decorating consultant and travel to people's houses to do the work there, but you'd have to check!