Gearbox help

I have just bought a 57 plate A4 2L Sline (diesel) and it has a multitronic gearbox. I have only ever driven manual before so I am not sure if it is behaving as it should be?

When it needs to change up gear it revs really high before changing into the next gear, so for example this morning I was doing 40 on the motorway and it was in third for what seemed like ages, it does eventually change but I know in my manual I would have changed it a lot sooner than the car does.

So I then decided to drive it in Manual I felt a lot more comfortable changing up a gear before it reached 2500 revs. However I noticed that when I slowed down the car changed down gear even whilst in manual mode

so my two questions are

1 - when in auto it is the norm for it to change gear at what I feel to be a lot later than it should

2 - is it correct that it will change down gear when I reduce speed even when in manual mode?

my hubby thinks it is because I used to drive in quite a high gear at lower speeds but I have driven a six speed car for nine years now and my car would happily cruise at 50 miles an hour in 6th