Real Estate / Building in Poland, house builders quote prices with foundations? [8]

Hi all,

Have not posted for a while but see the place has not changed much. Looking for some helpful advice with regard to building in Poland 100m2 - 150 m2. My partner and I are considering building in Poland in the south just outside of Lublin. We have land to build on which has planning consent for a single house, and after looking at the land and speaking with people in the area, there is already mains gas, electric and waste on site. Have been looking at plans and costs for building which seem reasonable for the size of property we are considering. I have a few questions which I hope some people here might be able to help with or point me in the direction of where I can source some help.

Where house builders quote prices does this typically include the foundations, and assume flat ground? (I know this is a vague question)
The term "Stan surowy zamkniety " does this basically mean "first fit" or is it just a shell, with windows/doors and the mains supply into the house for gas, water and electricity?

Are there any legal implication for someone in the UK building and owning a house in Poland?

What are the other basic pitfalls, people tebnd to forget about when planning this? We are going into this with our eyes open and we are purely at the planning stage at the moment although we could potentially start next spring building but with a timeframe of around 2 years for completion.

Thanks in advance