2012 Volvo D50 Rough Idle, ECU relearn?

[clfurness]

Hi, I've got a 2012 registered Volvo V50 (with the D2 Engine - if this makes any odds?)

After two different mechanics had my car, I had the same problem as you with a really rough idle. The car did pick up at higher revs though. They thought it was something to do with the injectors, a valve or a gasket. However, I knew from previous experience that the car's ECU could have been reset. I took it out for a 20+ mile drive going between 1500rpm, then flooring it to 2500rpm before letting off completely.
After a few cycles, the engine started to improve, and by the end of the drive the idel was as smooth as any, even when starting cold.

Now, I've reset the learning twice so I know the procedure is at least a quick fix. Does anyone know if this is correct?
What actually causes the reset, and why does it happen everytime someone plugs my car in for diagnostics?

I think I'll get a dealer to do the diagnostic to check if there are any faults to check out, but will this reset my remapping?
(no the remapping didn't cause the initial problem as it was remapped after the learning had been reset and relearned)