I have always had the worst time with keys. If they don't work I only make them worse. My German partner on the other hand takes half of those cases and gets them to turn one more time. Getting them to turn one more time makes replacement simple with the tools mentioned above.
I am not as familiar with the 201 chassis steering lock as I haven't actually done that kind of work since before they were born (or at least since before they started to break). On other cars such as the 126/123 chassis we would drill the pin that must be pushed to remove the steering lock from the column. It is the only metal that is soft enough to drill. Once off the column (but still held by the wiring), we used a carbide wheel to make three small slices to cut the screws that hold the electrical switch to the rear. This allowed the thing to be put in a vice for further slicing. Through the years we have come to the conclusion that both the steering lock and tumbler should be replaced so we now just throw the whole thing out once removed.
As to the locksmiths who drill the thing apart. I have a three page document out of a locksmith manual that describes the procedure (we have never been successful trying it, but haven't tried more than once or twice). The concept is to drill through the open key slot with a small enough drill to pass through. The idea is to open a cavity below the pin that can't be depressed (until the lock tumbler is in the proper position). The only possible way to do this would be to have new parts in hand and visualize this exact place (and visualize what you are trying to achieve).
Bosch Master, ASE Master, L1
33 years MB technician