Hi QDM,
1. The trip was a lot of fun. 2 DR400's, 8 people, 12 flying hours each in 3 days, and only a couple of scary moments! (Newly qualified PPL who rotated a fully-laden aircraft just the way he does when he's on his own....
, and another chap who thought he could rescue a ghastly approach into a short strip. Gave me my first ever "I have control" moment as I did the go around for him...
)
The English ATC was OK, except for London info, who stressed them... I'm sure the chap who was on duty noticed it was my voice that answered, whether he called me or my friends - but he didn't say anything.
2. My thoughts on DR400 vs D140:
D140 is nicer to fly. Lighter controls, and more responsive. It's better for rough strips, and seems better at high altitude (although I haven't flown the 180hp DR400 to compare). It's got a wider cabin, and better visibility - no painted roof. It's also got a hugely bigger (and separate) luggage compartment - unless you go for the "Abeille" model.
On the other hand, the DR400 is more comfortable, has adjustable seats, doesn't leak in the rain, doesn't have a canopy that is prone to opening in flight if you haven't latched it carefully, has more places for storing maps and assorted junk, goes faster, has disc brakes and has two throttles so you can fly right-handed. It's also much easier to land, although the DR140 is about as easy a tail-dragger as you could hope to fly. You can probably get D400 parts rather more easily than D140.
The clincher for me is that you can put skis on a D140! A friend of mine is selling a particularly nice example, and I'm sorely tempted....