As a result of a re-categorisation as a Professional Client, you may lose the right of access to the Financial Ombudsman Service (see DISP 2.7.9 in the FCA Rules). Access to the FOS will not extend to all professional clients (only those that meet the FCA Handbook definition of a consumer) and may therefore not extend to you.
The FSCS compensation fund designed by the UK government to act as a ‘safety net’ only covers retail clients and small businesses if they’ve been clients of a financial services firm which becomes insolvent.