You aren't required to do any courses to operate drones commercially, however, you will need commercial drone insurance
From the 31st December 202, you are no longer required to hold a Permission for Commercial Operation from the CAA to fly drones for commercial use.
You are, however, mandated to hold commercial drone insurance. You can get commercial drone insurance from specialist companies such as Coverdrone.
Although you don't need to do a course to operate commercially you may need to do a course to fly your drones (if over 250g in weight) in built-up areas (areas used for residential, commercial, industrial and recreational purposes).
If you fly relatively small drones you might want to consider the A2 Certificate of Competency (ideal for people who Operate DJI Mavic, Mavic Air, Phantoms etc).
If you fly larger drones, or, if you want to fly over uninvolved people then you might need the more professional qualification the General Visual Line fo Sight Certificate.