A quick post to report on a 3 week trip I have just completed with my 2 kids. We crossed to Calais, drove through Belgium to Germany, down to Switzerland, across to France, into Spain and Andorra, then back through France. Just over 4,500 Kms in total and the Bongo performed amazingly. Not a single fault except for what I thought was a hook up problem and must have been a bad adapter as it is working fine now I am back in the UK. The Alps were no problem (travelling mainly through the tunnels!) but the Pyrenees were a bit of an effort at times, probably because I was reluctant to put my foot down and see the petrol gauge go down at the same rate as the speedo went up!
We had an absolutely brilliant time and if anyone is taking a similar route I can recommend some campsites we stayed at on the way, along with some great places to visit. I have a part converted V6 AFT, with single rear seats and bed boards in the roof and although it was a bit squashed at times, this could have been improved by (1) taking a bit less stuff and (2) slightly better use of space in the back (I have a few plans for the winter).
I kept quite a detailed diary and updated the content to my blog, so there are plenty of pictures and information about the itinerary if you are interested. http://www.stuffaboutjames.wordpress.com
I was always on the lookout but didn't see a single other Bongo in mainland Europe

Cheers
Jimone