Hi there. Although I don't match up with your criteria for requesting a reply. I thought I would give you my general opinion. I regularly travel with a disabled relative on Tui flights/cruises.
Are you aware that you are entitled to free seats on the flight. If I use a TA they ring special assistance and request whatever I need, plus the free seats. If I book myself online I send an email to special assistance and do the request myself.
Never been let down by them yet. Maybe of some help hopefully