Probably the most difficult air filter in the world to change.
Usually there is a plastic box with a few hooks securing the lid. You simply open it, remove the old air filter and put a new one it.
Hardly 5 minutes.
However, BMW have decided to do something different.
To gain access to the air filter, it is a step-wise approach.

1. Remove the front plastic cover.
2. Then remove the corrugated pipe leading to the rear plastic cover (the air filter housing).
3. Now remove the cabin filter (a) by rotating the three circular clips (b) anti-clockwise and pulling it out.
4. Remove the cabin filter housing (c) by opening the 4 screws on the back.
5. Before taking it out, make sure to disconnect the clip (d) that holds the three pipes (e) running across, taking care not to damage them.
6. Now open the 4 nuts on the rear plastic cover with a hex screwdriver. You can see one of them (f) in the picture. There is one beneath the cabin filter housing (which you should have removed by now). The other two are hidden on the driver's side.
7. You need to ensure not to drop any of the nuts or the screwdriver bit as it will fall on the plastic cover underneath the engine bay. (I dropped one but luckily pulled it with a magnetic wire.)
8. Once the four nuts are out of the way remove the plastic cover (g) carefully by manipulating it against the three pipes (e).
9. Remove the old air filter by pulling it towards the rear of the car.
10. Fix the new air filter (approx £15).
11. Reverse the above steps.

Oil and oil filter

Quite easy, to be honest. You'll need 36 mm and 17 mm bits to open the oil filter housing and sump plug, respectively.

1. Make sure that the car is level and the engine is warm.
2. If you have reasonable ground clearance no real need to jack the car up. If you do, do not use the car jack as it’s extremely unstable.
3. The sump plug is in the midline just behind a circular metallic thing. It should be covered by a square-ish plastic window which is part of the plastic tray. Therefore, no need to dismantle, or remove, the tray.
4. Open the sump plug (17 mm).
5. The oil will be quite hot so be careful while catching it in an appropriate dish.
6. Open the oil filter housing (36 mm) carefully (h) and also remove the dipstick (i) and the lid (j) from where you’ll pour the new oil in.
7. Remove the old oil filter.
8. Clean the housing (h) carefully.
9. Replace whatever rubber washers are supplied with the new filter (approx £5).
10. Re-fit the oil filter, you may want to 'prime' it by filling the housing with new oil. If you do, make sure that you have closed the sump first.
11. Clean the dipstick and put it back in.
12. Fit the sump plug and if a copper washer was part of the new filter, replace that as well.
13. Fill with 5 litres of 0W or 5W synthetic oil (approx £20 for Comma). You may check in your handbook if a different amount or grade of oil is required.
14. Drive gently for the first few miles.

I’ve read mixed views about using engine flushes (including a few horror stories) but at the end decided to use one. It was from STP, cost only £3.25 and I strictly followed the instructions, i.e.,