Hi there,
The V6 petrol has a flat panel air filter under the drivers seat by the chassis. It's in a black plastic box which is undone by 4 spring clips. Easy to change.
Oil filter is on the lower side of the engine under the passenger seat, you can access this from below without removing the undertray, but put an ice cream container below first as a small amount of oil will spill out as you remove it.
Take a look at lushprojects, this has good diagrams of the car and engine.
http://www.lushprojects.com/bongopartsmk2/
Hope this helps.
Andy