Bryn,
No need to worry at all about Dethleffs. We bought a DL540 at Earls Court 2005 and have been very pleased with it. Yes, we had acouple of small faults with it at first but nothing like some of the horror stories you read about on this forum.
Only problem is lack of dealers, we have to travel 200miles to get annual service done to comply with warranty terms when we have a very good workshop only two miles away!.
In all they are pretty well built, very comfortable and with the BPW chassis tow very well indeed.
Graham F