Cleaning the column switching out is a must do - if they've not been done for a long time, they can be a right filth and fluff magnet. Many issues can be sorted by ensuring the unit is as clean as you can reasonably get it. Also, check the various solder points for any evidence of wear. I've had intermittent issues with the wire for the dipped beams (which is soldered to the underside of the switch unit) coming away. This is, IMO, partially due to usage/current, but also because the wire is at a very tight angle and tension is pulling the solder away. At some point, I need to take the unit off and look at replacing that wire entirely to give a bit more slack and solder it on the bench rather than in situ in the car!