I'm a third-country national who is a self-employed permanent resident in the Czech Republic. As far as I'm aware, EU companies are free to post workers to other EU countries, even if those workers are non-EU citizens. I am also aware that even non-EU companies regularly send out their employees to the EU for "business meetings", which can include some degree of work done on-site for the parent company.
Being a self-employed software engineering consultant, am I allowed to sign a contract with a company located in the UK (signed by myself as a business, not as a physical person) and then proceed to travel to the UK visa-free to work for said company as an external employee? My passport allows me visa-free access to the UK, so normally I won't need to apply for an entry clearance beforehand.
Links to official UK government websites explaining the limits to what an EU contractor may do within the UK (without a work permit) would be appreciated. I am aware that Brexit would complicate things in the future, but for now all previous EU laws are still in effect.