Fuji,
I'm surprised at you encouraging these people to do this. No disrespect to Backpacker and friend but, the clues were in the question...
low hours ppl and "long trip". Sorry, cross channel, even SAM - MP isn't a long trip for most.
There's enough to do if its your first X channel... without switching freqs to talk to your mate.. you should know how busy London will be if the conditions are good vfr as described in the question. Also mid channel, talking to London, getting the LFAT Atis, joining in with the 1000 other people over Bolougne isn't the time to be giving your mate a teach in on Box 2.
If you want to show him, fly together in one plane first.
Rant over.