Hello, have a look at "hello from germany - rhein-main-area"... I've (and my wife) done 2000 KM in 4 days. Most time in bad weather. The last day was 700 KM on the motorway. The days before were in south britian with one day Southampthon - LandsEnd, most on the M30, one day LandsEnd -Lymington via Dartmoor. My wife told me the +4 is a comfortable car for such travelling.
Look forward to enjoy your journey!
Greets from Germany
René