When we went to France last year (pre-Rosie) I was taking note of the way that they transported pets - it was about a four hour journey and dogs were left in the boot of the car! You were allowed back down to check on them, but onyl a couple of times. That was Portsmouth to Cherbourg, so I guess there are much shorter routes.
I'm not sure I fancy the idea of putting her in the hold of an aeroplane just for a holiday. I presume that they have to be boxed up for a very long time - check in and loading and flight then going through Customs etc at the other end. I think kennels woudl be less stressful.