What are peoples experinces with large conversions?

Over the past few days there has been several people on another site(PTS) whom have reported that they have converted large amounds to BA Miles(or Airmiles) & these have been 'frozen' whilst they are being security checked.

It appears they may be less strict with BA Miles conversions however it would be good to hear peoples experieces here(of recent conversions of £350 & upwards). I plan on making several large conversions soon and i would rather not have my account security checked so i am trying to harvest as much information as is possible.