Thanks Chilli, ATCO, LH2, eastern. At least you confirmed my suspicion that the UK is different from mainland Europe & Ireland. I'll probably be asking London Info to close my flightplan anyway when coming from abroad despite the fact that I now know I get a meaningless "roger" back. Just to cover my ass if somebody outside the UK decides to launch a SAR anyway :-)
I had a few other questions in my original post. Among others, does it make sense to put an elaborate route in a VFR flightplan? Is anybody reading this in case of VFR? Does it increase my chances of getting a transition through controlled airspace en-route? And if so, how do I do this if I "Follow Roads"?