Hello Pro55,
The price you've been quoted is similar to that mentioned in my 3rd post above.
Yes, I was also told the micro filter gets replaced every service. I'll be doing this while the car is on BSI but after that, I'll be cleaning it myself and getting it replaced every 2nd or 3rd service.
The micro filter cleans the air going through the a/c system. It has several layers of filter fabric and a layer of charcoal to remove odours. I usually have the air re circulation mode activated because I can still smell fumes from trucks, or in tunnels, or from some older model cars. This tells me the filters aren't that effective at removing odours ... it also tells me CO
2 is coming into the car .... ergo, the re circulation mode is active for urban and suburban areas.
Cleaning the filters is pretty straight forward.
Here's a link to a step by step guide to changing your own filters.
I suggest you remove the filters, vacuum the intake side only with low pressure vacuum, and reinstall. If you think the charcoal is worthwhile but ineffective then replace the filters.
This is my first X5, but I've owned a 330d and a 530d. I did my own filters in both cars.
Good luck.