Backpacker sums it up very well..
For a new or say 10 hours+ PPL, there's so much more to learn and take in about flying Cross Channel.
I found the best way to do it was to get in a plane with 2 more experienced pilots and let myself be guided by them.
The benefit of doing it with more experienced other pilots is we didn't have to pick the shortest channel crossing point, we coasted out from Hastings right over towards Dieppe and went half way down France.
A great learning experience and I got 3 hours P1 and the chance to fly in a very nice PA28 Archer III.
I found also, that when I did take my girlfriend up as soon as I'd passed, that a 20 minute trip locally for some lunch was more than enough to make for a good day out, but short enough so that if she didnt like it we'd have been quickly back to base.