In the US, it is usually free, but you are not in the US. As it was a TSB, not a recall, it is optional for dealers to even tell you about it or admit it exists or apply it even though it was highly recommended and all were notified by Honda corporate. NHTSA also made the public aware of it, as you saw. This is based on my experience being in the US and dealing with both recalls and TSBs. Is there an equivalent to the NHTSA (National Highway Traffic Safety Administration) there, if so check their web page or contact them.
Sounds typical for a fixed rate "repair/check/diagnosis". I bet all dealers will be similar, but contact Honda directly and ask about that software update(TSB) and if it applies to your year and market. If it does, ask Honda if it is free or if you should get a charge for it. If you were in the US and going to a dealer, I would print out the appropriate TSB and talk to the service writer and service manager about getting it applied. But you are not, and everywhere is different. The one I linked to contains all the details and processes for the dealer. Per that TSB should take less than 0.3 hr and is charged? Again, this presumes it is the right Service Bulletin and is appropriate for your car and region.
My local Honda dealership wants almost €100 ($105) for checking if my CR-Z needs a software update. Is that normal? I thought/hoped something like that would be free.