421C,
I can see how that might be acceptable depending on aircraft range.
If for example weather in the UK was good, Northern France poor, and Mid and Southern France CAVOK then I can understand how you could justify that. In all fairness in such a circumstance your chances of getting caught out aren't very high.
However often such bands of poor weather can be associated with a front, and your average light aircraft doesn't come equipped with the oxygen system nor performance to climb over frontal system.
But actaully I find the biggest problem with flying on top is airspace. If you fly towards airspace and can't get a clearance through (Damn class A all over the UK!
) your option of desending to go under is gone because of the undercast. Admittedly that's not such a big problem in France, but can be with militiary areas.
Your average PA28 or C172 has a (safe) range not much more than 4 hours. If you plan a three hour trip and you spend an hour in good weather, an hour over an overcast, and then the clearer weather doesn't materalise for the last hour of your trip, you find yourself in a rather difficult situation. Do you press on hoping that it will get better, or return back while you still have sufficient fuel?
For these reasons I don't believe may VFR pilots will put themselves into a situation where they don't have the option of desending.
I keep asking myself how the conversation would go with the authorities. I can imagine them saying:
"The forecast for your destination was SCT and BKN for the whole day. What was your backup plan if the actual turned out to be a bit worse than forecast and it was overcast?"
If your answer is to make an illegal approach because you knew you could do it safely, I suspect they might not be happy with your reliance on forecasts at the planning stage.
If your backup plan was something more sensible like divert, or return to an area of known good weather, or return to base, then I think they would not unreasonably ask why you didn't execute that plan.
dp